Index: binaries/data/mods/public/gui/common/tooltips.js
===================================================================
--- binaries/data/mods/public/gui/common/tooltips.js
+++ binaries/data/mods/public/gui/common/tooltips.js
@@ -407,12 +407,25 @@
 		});
 	}
 
+	let stackabilityString = "";
+	if (template.Stackability && template.Stackability != "Ignore")
+	{
+		tooltipAttributes.push("%(stackability)s");
+		if (template.Stackability == "Extend")
+			stackabilityString = translateWithContext("status effect stackability", "(extends)");
+		else if (template.Stackability == "Replace")
+			stackabilityString = translateWithContext("status effect stackability", "(replaces)");
+		else if (template.Stackability == "Stack")
+			stackabilityString = translateWithContext("status effect stackability", "(stacks)");
+	}
+
 	return sprintf(translate("%(statusName)s: " + tooltipAttributes.join(translate(commaFont(", ")))), {
 		"statusName": headerFont(translateWithContext("status effect", template.Name)),
 		"tooltip": tooltipString,
 		"effects": attackEffectsString,
 		"rate": intervalString,
-		"duration": durationString
+		"duration": durationString,
+		"stackability": stackabilityString
 	});
 }
 
Index: binaries/data/mods/public/gui/session/selection_details.js
===================================================================
--- binaries/data/mods/public/gui/session/selection_details.js
+++ binaries/data/mods/public/gui/session/selection_details.js
@@ -108,7 +108,9 @@
 			size.top = i * 18;
 			size.bottom = i * 18 + 16;
 			statusIcons[i].size = size;
-			i++;
+
+			if (++i >= statusIcons.length)
+				break;
 		}
 		for (; i < statusIcons.length; ++i)
 			statusIcons[i].hidden = true;
Index: binaries/data/mods/public/gui/session/selection_panels_middle/single_details_area.xml
===================================================================
--- binaries/data/mods/public/gui/session/selection_panels_middle/single_details_area.xml
+++ binaries/data/mods/public/gui/session/selection_panels_middle/single_details_area.xml
@@ -83,7 +83,7 @@
 				<translatableAttribute id="tooltip">Rank</translatableAttribute>
 			</object>
 
-			<!-- Status Effecst icons -->
+			<!-- Status Effects icons -->
 			<object  name="statusEffectsIcons" size="100%-20 4 100%-4 100%">
 				<repeat count="5">
 					<object type="image" size="0 0 16 16" z="200" tooltip_style="sessionToolTip"/>
Index: binaries/data/mods/public/simulation/components/StatusEffectsReceiver.js
===================================================================
--- binaries/data/mods/public/simulation/components/StatusEffectsReceiver.js
+++ binaries/data/mods/public/simulation/components/StatusEffectsReceiver.js
@@ -46,14 +46,30 @@
  *
  * @param {string} statusName - The name of the status effect.
  * @param {object} data - The various effects and timings.
+ * @param {object} attackerData - The attacker and attackerOwner.
  */
 StatusEffectsReceiver.prototype.AddStatus = function(statusName, data, attackerData)
 {
 	if (this.activeStatusEffects[statusName])
 	{
-		// TODO: implement different behaviour when receiving the same status multiple times.
-		// For now, these are ignored.
-		return;
+		if (data.Stackability == "Ignore")
+			return;
+		if (data.Stackability == "Extend")
+		{
+			this.activeStatusEffects[statusName].Duration += data.Duration;
+			return;
+		}
+		if (data.Stackability == "Replace")
+			this.RemoveStatus(statusName);
+		else if (data.Stackability == "Stack")
+		{
+			let i = 0;
+			let temp;
+			do
+				temp = statusName + "_" + ++i;
+			while (!!this.activeStatusEffects[temp]);
+			statusName = temp;
+		}
 	}
 
 	this.activeStatusEffects[statusName] = {};
Index: binaries/data/mods/public/simulation/components/tests/test_StatusEffectsReceiver.js
===================================================================
--- binaries/data/mods/public/simulation/components/tests/test_StatusEffectsReceiver.js
+++ binaries/data/mods/public/simulation/components/tests/test_StatusEffectsReceiver.js
@@ -1,5 +1,12 @@
+Engine.LoadHelperScript("MultiKeyMap.js");
+Engine.LoadHelperScript("Player.js");
+Engine.LoadHelperScript("ValueModification.js");
+Engine.LoadComponentScript("interfaces/Health.js");
+Engine.LoadComponentScript("interfaces/ModifiersManager.js");
 Engine.LoadComponentScript("interfaces/StatusEffectsReceiver.js");
 Engine.LoadComponentScript("interfaces/Timer.js");
+Engine.LoadComponentScript("Health.js");
+Engine.LoadComponentScript("ModifiersManager.js");
 Engine.LoadComponentScript("StatusEffectsReceiver.js");
 Engine.LoadComponentScript("Timer.js");
 
@@ -68,7 +75,7 @@
 	};
 	Engine.RegisterGlobal("Attacking", Attacking);
 
-	// damage scheduled: 0, 1, 2, 10 sec
+	// Damage scheduled: 0, 1, 2, 10 seconds.
 	cmpStatusReceiver.ApplyStatus({
 		"Burn": {
 			"Duration": 20000,
@@ -110,7 +117,7 @@
 	};
 	Engine.RegisterGlobal("Attacking", Attacking);
 
-	// damage scheduled: 0, 10, 20 sec
+	// Damage scheduled: 0, 10, 20 seconds.
 	cmpStatusReceiver.AddStatus(statusName, {
 		"Duration": 20000,
 		"Interval": 10000,
@@ -133,3 +140,203 @@
 }
 
 testRemoveStatus();
+
+function testModificationStatus()
+{
+	setup();
+
+	AddMock(target, IID_Identity, {
+		"GetClassesList": () => ["AffectedClass"]
+	});
+	let cmpModifiersManager = ConstructComponent(SYSTEM_ENTITY, "ModifiersManager");
+
+	let maxHealth = 100;
+	AddMock(target, IID_Health, {
+		"GetMaxHitpoints": () => ApplyValueModificationsToEntity("Health/Max", maxHealth, target)
+	});
+
+	let statusName = "Haste";
+	let factor = 0.5;
+	cmpStatusReceiver.AddStatus(statusName, {
+		"Duration": 5000,
+		"Modifiers": {
+			[statusName]: {
+				"Paths": {
+					"_string": "Health/Max"
+				},
+				"Affects": {
+					"_string": "AffectedClass"
+				},
+				"Multiply": factor
+			}
+		}
+	},
+	{
+		"entity": enemyEntity,
+		"owner": enemy,
+	});
+
+	let cmpHealth = Engine.QueryInterface(target, IID_Health);
+	// Test that the modification is applied.
+	TS_ASSERT_EQUALS(cmpHealth.GetMaxHitpoints(), maxHealth * factor);
+	cmpTimer.OnUpdate({ "turnLength": 1 });
+	TS_ASSERT_EQUALS(cmpHealth.GetMaxHitpoints(), maxHealth * factor);
+
+	// Test that the modification is removed after the appropriate time.
+	cmpTimer.OnUpdate({ "turnLength": 4 });
+	TS_ASSERT_EQUALS(cmpHealth.GetMaxHitpoints(), maxHealth);
+}
+
+testModificationStatus();
+
+function applyStatus(stackability)
+{
+	cmpStatusReceiver.ApplyStatus({
+		"Burn": {
+			"Duration": 3000,
+			"Interval": 1000,
+			"Damage": {
+				"Burn": 1
+			},
+			"Stackability": stackability
+		}
+	});
+}
+
+function testStackabilityIgnore()
+{
+	setup();
+	let Attacking = {
+		"HandleAttackEffects": (_, attackData) => {
+			if (attackData.Damage.Burn) dealtDamage += attackData.Damage.Burn;
+		},
+	};
+	Engine.RegisterGlobal("Attacking", Attacking);
+
+	applyStatus("Ignore");
+
+	// 1 Second: 1 update and lateness.
+	cmpTimer.OnUpdate({ "turnLength": 1 });
+	TS_ASSERT_EQUALS(dealtDamage, 2);
+
+	applyStatus("Ignore");
+
+	// 2 Seconds.
+	cmpTimer.OnUpdate({ "turnLength": 1 });
+	TS_ASSERT_EQUALS(dealtDamage, 3);
+
+	// 3 Seconds: finished in previous turn.
+	cmpTimer.OnUpdate({ "turnLength": 1 });
+	TS_ASSERT_EQUALS(dealtDamage, 3);
+}
+
+function testStackabilityExtend()
+{
+	setup();
+	let Attacking = {
+		"HandleAttackEffects": (_, attackData) => {
+			if (attackData.Damage.Burn) dealtDamage += attackData.Damage.Burn;
+		},
+	};
+	Engine.RegisterGlobal("Attacking", Attacking);
+
+	applyStatus("Extend");
+
+	// 1 Second: 1 update and lateness.
+	cmpTimer.OnUpdate({ "turnLength": 1 });
+	TS_ASSERT_EQUALS(dealtDamage, 2);
+
+	applyStatus("Extend"); // +3 Seconds.
+
+	// 2 Seconds.
+	cmpTimer.OnUpdate({ "turnLength": 1 });
+	TS_ASSERT_EQUALS(dealtDamage, 3);
+
+	// 3 Seconds: extended in previous turn.
+	cmpTimer.OnUpdate({ "turnLength": 1 });
+	TS_ASSERT_EQUALS(dealtDamage, 4);
+
+	// 4 Seconds.
+	cmpTimer.OnUpdate({ "turnLength": 1 });
+	TS_ASSERT_EQUALS(dealtDamage, 5);
+
+	// 5 Seconds.
+	cmpTimer.OnUpdate({ "turnLength": 1 });
+	TS_ASSERT_EQUALS(dealtDamage, 6);
+
+	// 6 Seconds: finished in previous turn (3 + 3).
+	cmpTimer.OnUpdate({ "turnLength": 1 });
+	TS_ASSERT_EQUALS(dealtDamage, 6);
+}
+
+function testStackabilityReplace()
+{
+	setup();
+	let Attacking = {
+		"HandleAttackEffects": (_, attackData) => {
+			if (attackData.Damage.Burn) dealtDamage += attackData.Damage.Burn;
+		},
+	};
+	Engine.RegisterGlobal("Attacking", Attacking);
+
+	applyStatus("Replace");
+
+	// 1 Second: 1 update and lateness.
+	cmpTimer.OnUpdate({ "turnLength": 1 });
+	TS_ASSERT_EQUALS(dealtDamage, 2);
+
+	applyStatus("Replace");
+
+	// 2 Seconds: 1 update and lateness of the new status.
+	cmpTimer.OnUpdate({ "turnLength": 1 });
+	TS_ASSERT_EQUALS(dealtDamage, 4);
+
+	// 3 Seconds.
+	cmpTimer.OnUpdate({ "turnLength": 1 });
+	TS_ASSERT_EQUALS(dealtDamage, 5);
+
+	// 4 Seconds: finished in previous turn.
+	cmpTimer.OnUpdate({ "turnLength": 1 });
+	TS_ASSERT_EQUALS(dealtDamage, 5);
+}
+
+function testStackabilityStack()
+{
+	setup();
+	let Attacking = {
+		"HandleAttackEffects": (_, attackData) => {
+			if (attackData.Damage.Burn) dealtDamage += attackData.Damage.Burn;
+		},
+	};
+	Engine.RegisterGlobal("Attacking", Attacking);
+
+	applyStatus("Stack");
+
+	// 1 Second: 1 update and lateness.
+	cmpTimer.OnUpdate({ "turnLength": 1 });
+	TS_ASSERT_EQUALS(dealtDamage, 2);
+
+	applyStatus("Stack");
+
+	// 2 Seconds: 1 damage from the previous status + 2 from the new (1 turn + lateness).
+	cmpTimer.OnUpdate({ "turnLength": 1 });
+	TS_ASSERT_EQUALS(dealtDamage, 5);
+
+	// 3 Seconds: first one finished in the previous turn, +1 from the new.
+	cmpTimer.OnUpdate({ "turnLength": 1 });
+	TS_ASSERT_EQUALS(dealtDamage, 6);
+
+	// 4 Seconds: new status finished in previous turn.
+	cmpTimer.OnUpdate({ "turnLength": 1 });
+	TS_ASSERT_EQUALS(dealtDamage, 6);
+}
+
+function testStackability()
+{
+	testStackabilityIgnore();
+	testStackabilityExtend();
+	testStackabilityReplace();
+	testStackabilityStack();
+}
+
+testStackability();
Index: binaries/data/mods/public/simulation/data/technologies/advanced_unit_bonus.json
===================================================================
--- binaries/data/mods/public/simulation/data/technologies/advanced_unit_bonus.json
+++ binaries/data/mods/public/simulation/data/technologies/advanced_unit_bonus.json
@@ -23,7 +23,9 @@
 		{ "value": "Loot/wood", "multiply": 1.2 },
 		{ "value": "Loot/stone", "multiply": 1.2 },
 		{ "value": "Loot/metal", "multiply": 1.2 },
-		{ "value": "Loot/xp", "multiply": 1.2 }
+		{ "value": "Loot/xp", "multiply": 1.2 },
+		{ "value": "Attack/Ranged/ApplyStatus/Bogus/Duration", "multiply": 2 },
+		{ "value": "Attack/Ranged/ApplyStatus/AnotherBogus/Modifiers/Resiliance/Add", "multiply": 2 }
 	],
 	"affects": ["Advanced Unit", "Elite Unit"]
 }
Index: binaries/data/mods/public/simulation/helpers/Attacking.js
===================================================================
--- binaries/data/mods/public/simulation/helpers/Attacking.js
+++ binaries/data/mods/public/simulation/helpers/Attacking.js
@@ -26,6 +26,14 @@
 				"<anyName/>" +
 				"<interleave>" +
 					"<element name='Name'><text/></element>" +
+					"<element name='Stackability' a:help='How this status effect stacks. Choices are: \"Ignore\", which means nothing happens, \"Extend\", which means the duration is added to the currently applied status effect, \"Replace\", which means the currently active status effect is removed and the new one is put in place and \"Stack\", which means that the status effect is added multiple times.'>" +
+						"<choice>" +
+							"<value>Ignore</value>" +
+							"<value>Extend</value>" +
+							"<value>Replace</value>" +
+							"<value>Stack</value>" +
+						"</choice>" +
+					"</element>" +
 					"<optional>" +
 						"<element name='Icon' a:help='Icon for the status effect.'><text/></element>" +
 					"</optional>" +
@@ -106,7 +114,40 @@
 		ret.Capture = ApplyValueModificationsToEntity(valueModifRoot + "/Capture", +(template.Capture || 0), entity);
 
 	if (template.ApplyStatus)
-		ret.ApplyStatus = template.ApplyStatus;
+	{
+		ret.ApplyStatus = {};
+		for (let effect in template.ApplyStatus)
+		{
+			let statusTemplate = template.ApplyStatus[effect];
+			ret.ApplyStatus[effect] = {
+				"Name": statusTemplate.Name,
+				"Tooltip": statusTemplate.Tooltip,
+				"Duration": ApplyValueModificationsToEntity(valueModifRoot + "/ApplyStatus/" + effect + "/Duration", +(statusTemplate.Duration || 0), entity),
+				"Interval": ApplyValueModificationsToEntity(valueModifRoot + "/ApplyStatus/" + effect + "/Interval", +(statusTemplate.Interval || 1000), entity),
+				"Stackability": statusTemplate.Stackability
+			};
+			Object.assign(ret.ApplyStatus[effect], this.GetAttackEffectsData(valueModifRoot + "/ApplyStatus" + effect, statusTemplate, entity));
+			if (statusTemplate.Modifiers)
+			{
+				let modifiers = {};
+				for (let modifier in statusTemplate.Modifiers)
+				{
+					let modifierTemplate = statusTemplate.Modifiers[modifier];
+					modifiers[modifier] = {
+						"Paths": modifierTemplate.Paths,
+						"Affects": modifierTemplate.Affects
+					};
+					if (modifierTemplate.Add)
+						modifiers[modifier].Add = ApplyValueModificationsToEntity(valueModifRoot + "/ApplyStatus/" + effect + "/Modifiers/" + modifier + "/Add", +(modifierTemplate.Add || 0), entity);
+					if (modifierTemplate.Multiply)
+						modifiers[modifier].Multiply = ApplyValueModificationsToEntity(valueModifRoot + "/ApplyStatus/" + effect + "/Modifiers/" + modifier + "/Multiply", +(modifierTemplate.Multiply || 0), entity);
+					if (modifierTemplate.Replace)
+						modifiers[modifier].Replace = modifierTemplate.Replace;
+				}
+				ret.ApplyStatus[effect].Modifiers = modifiers;
+			}
+		}
+	}
 
 	if (template.Bonuses)
 		ret.Bonuses = template.Bonuses;
Index: binaries/data/mods/public/simulation/templates/template_unit_infantry_ranged_archer.xml
===================================================================
--- binaries/data/mods/public/simulation/templates/template_unit_infantry_ranged_archer.xml
+++ binaries/data/mods/public/simulation/templates/template_unit_infantry_ranged_archer.xml
@@ -11,6 +11,51 @@
         <Pierce>6.0</Pierce>
         <Crush>0</Crush>
       </Damage>
+      <ApplyStatus>
+        <Bogus>
+          <Name>StatusEffect's name 1</Name>
+          <Stackability>Extend</Stackability>
+          <Tooltip>Some bogus bonus tooltip describing the effect of the modifiers. This speeds up the entity but halves the health and resource gathering speed.</Tooltip>
+          <Duration>15000</Duration>
+          <Modifiers>
+            <Haste>
+              <Paths datatype="tokens">UnitMotion/WalkSpeed</Paths>
+              <Affects datatype="tokens">Unit</Affects>
+              <Add>20</Add>
+            </Haste>
+            <Health>
+              <Paths datatype="tokens">Health/Max ResourceGatherer/BaseSpeed</Paths>
+              <Affects datatype="tokens">Unit Structure</Affects>
+              <Multiply>0.5</Multiply>
+            </Health>
+          </Modifiers>
+        </Bogus>
+        <Bogus2>
+          <Name>StatusEffect's name 2</Name>
+          <Stackability>Replace</Stackability>
+          <Duration>10000</Duration>
+          <Interval>1000</Interval>
+          <Damage>
+            <Poison>1</Poison>
+          </Damage>
+        </Bogus2>
+        <AnotherBogus>
+          <Name>StatusEffect's name 3</Name>
+          <Stackability>Stack</Stackability>
+          <Tooltip>Some bogus bonus tooltip describing the effect of the modifiers. This increases the armour permanently.</Tooltip>
+          <Interval>1000</Interval>
+          <Damage>
+            <Poisson>1</Poisson>
+          </Damage>
+          <Modifiers>
+            <Resiliance>
+              <Paths datatype="tokens">Armour/Hack Armour/Pierce Armour/Crush</Paths>
+              <Affects datatype="tokens">Unit</Affects>
+              <Add>20</Add>
+            </Resiliance>
+          </Modifiers>
+        </AnotherBogus>
+      </ApplyStatus>
       <MaxRange>72.0</MaxRange>
       <MinRange>0.0</MinRange>
       <PrepareTime>600</PrepareTime>