diff --git a/src/actor.h b/src/actor.h
index 6e0c625f1..9ae11696b 100644
--- a/src/actor.h
+++ b/src/actor.h
@@ -320,6 +320,8 @@ enum
 	MF6_SHATTERING		= 0x00020000,	// marks an ice corpse for forced shattering
 	MF6_KILLED			= 0x00040000,	// Something that was killed (but not necessarily a corpse)
 	MF6_BLOCKEDBYSOLIDACTORS = 0x00080000, // Blocked by solid actors, even if not solid itself
+	MF6_ADDITIVEPOISONDAMAGE	= 0x00100000,
+	MF6_ADDITIVEPOISONDURATION	= 0x00200000,
 
 // --- mobj.renderflags ---
 
@@ -505,7 +507,6 @@ enum
 	AMETA_BloodColor,		// colorized blood
 	AMETA_GibHealth,		// negative health below which this monster dies an extreme death
 	AMETA_WoundHealth,		// health needed to enter wound state
-	AMETA_PoisonDamage,		// Amount of poison damage
 	AMETA_FastSpeed,		// Speed in fast mode
 	AMETA_RDFactor,			// Radius damage factor
 	AMETA_CameraHeight,		// Height of camera when used as such
@@ -843,6 +844,15 @@ public:
 	AActor			*BlockingMobj;	// Actor that blocked the last move
 	line_t			*BlockingLine;	// Line that blocked the last move
 
+	int PoisonDamage; // Damage received per tic from poison.
+	int PoisonDuration; // Duration left for receiving poison damage.
+	int PoisonPeriod; // How often poison damage is applied. (Every X tics.)
+
+	int PoisonDamageReceived; // Damage received per tic from poison.
+	int PoisonDurationReceived; // Duration left for receiving poison damage.
+	int PoisonPeriodReceived; // How often poison damage is applied. (Every X tics.)
+	TObjPtr<AActor> Poisoner; // Last source of received poison damage.
+
 	// a linked list of sectors where this object appears
 	struct msecnode_t	*touching_sectorlist;				// phares 3/14/98
 
diff --git a/src/p_interaction.cpp b/src/p_interaction.cpp
index 7dfd7398f..d4db86436 100644
--- a/src/p_interaction.cpp
+++ b/src/p_interaction.cpp
@@ -1369,6 +1369,34 @@ dopain:
 		target->flags |= MF_JUSTHIT;    // fight back!
 }
 
+void P_PoisonMobj (AActor *target, AActor *inflictor, AActor *source, int damage, int duration, int period)
+{
+	int olddamage = target->PoisonDamageReceived;
+	int oldduration = target->PoisonDurationReceived;
+
+	target->Poisoner = source;
+
+	if (inflictor->flags6 & MF6_ADDITIVEPOISONDAMAGE)
+	{
+		target->PoisonDamageReceived += damage;
+	}
+	else
+	{
+		target->PoisonDamageReceived = damage;
+	}
+
+	if (inflictor->flags6 & MF6_ADDITIVEPOISONDURATION)
+	{
+		target->PoisonDurationReceived += duration;
+	}
+	else
+	{
+		target->PoisonDurationReceived = duration;
+	}
+
+	target->PoisonPeriodReceived = period;
+}
+
 bool AActor::OkayToSwitchTarget (AActor *other)
 {
 	if (other == this)
diff --git a/src/p_local.h b/src/p_local.h
index 387089f68..a69f2549d 100644
--- a/src/p_local.h
+++ b/src/p_local.h
@@ -480,6 +480,7 @@ extern FBlockNode**		blocklinks; 	// for thing chains
 //
 void P_TouchSpecialThing (AActor *special, AActor *toucher);
 void P_DamageMobj (AActor *target, AActor *inflictor, AActor *source, int damage, FName mod, int flags=0);
+void P_PoisonMobj (AActor *target, AActor *inflictor, AActor *source, int damage, int duration, int period);
 bool P_GiveBody (AActor *actor, int num);
 bool P_PoisonPlayer (player_t *player, AActor *poisoner, AActor *source, int poison);
 void P_PoisonDamage (player_t *player, AActor *source, int damage, bool playPainSound);
diff --git a/src/p_map.cpp b/src/p_map.cpp
index 34f396317..3ee9b15f2 100644
--- a/src/p_map.cpp
+++ b/src/p_map.cpp
@@ -1088,6 +1088,13 @@ bool PIT_CheckThing (AActor *thing, FCheckPosition &tm)
 						P_RipperBlood (tm.thing, thing);
 					}
 					S_Sound (tm.thing, CHAN_BODY, "misc/ripslop", 1, ATTN_IDLE);
+
+					// Do poisoning (if using new style poison)
+					if (tm.thing->PoisonDuration != INT_MIN)
+					{
+						P_PoisonMobj(thing, tm.thing, tm.thing->target, tm.thing->PoisonDamage, tm.thing->PoisonDuration, tm.thing->PoisonPeriod);
+					}
+
 					damage = tm.thing->GetMissileDamage (3, 2);
 					P_DamageMobj (thing, tm.thing, tm.thing->target, damage, tm.thing->DamageType);
 					if (!(tm.thing->flags3 & MF3_BLOODLESSIMPACT))
@@ -1109,6 +1116,13 @@ bool PIT_CheckThing (AActor *thing, FCheckPosition &tm)
 				return true;
 			}
 		}
+
+		// Do poisoning (if using new style poison)
+		if (tm.thing->PoisonDuration != INT_MIN)
+		{
+			P_PoisonMobj(thing, tm.thing, tm.thing->target, tm.thing->PoisonDamage, tm.thing->PoisonDuration, tm.thing->PoisonPeriod);
+		}
+
 		// Do damage
 		damage = tm.thing->GetMissileDamage ((tm.thing->flags4 & MF4_STRIFEDAMAGE) ? 3 : 7, 1);
 		if ((damage > 0) || (tm.thing->flags6 & MF6_FORCEPAIN)) 
@@ -3471,6 +3485,13 @@ AActor *P_LineAttack (AActor *t1, angle_t angle, fixed_t distance,
 						trace.Actor, srcangle, srcpitch);
 				}
 			}
+
+			// Allow puffs to inflict poison damage, so that hitscans can poison, too.
+			if (puffDefaults->PoisonDuration != INT_MIN)
+			{
+				P_PoisonMobj(trace.Actor, puff ? puff : t1, t1, puffDefaults->PoisonDamage, puffDefaults->PoisonDuration, puffDefaults->PoisonPeriod);
+			}
+
 			// [GZ] If MF6_FORCEPAIN is set, we need to call P_DamageMobj even if damage is 0!
 			// Note: The puff may not yet be spawned here so we must check the class defaults, not the actor.
 			if (damage || (puffDefaults->flags6 & MF6_FORCEPAIN))
@@ -3840,6 +3861,10 @@ void P_RailAttack (AActor *source, int damage, int offset, int color1, int color
 			P_TraceBleed (damage, x, y, z, RailHits[i].HitActor, source->angle, pitch);
 		}
 		if (spawnpuff) P_SpawnPuff (source, puffclass, x, y, z, source->angle - ANG90, 1, PF_HITTHING);
+
+		if (puffDefaults && puffDefaults->PoisonDuration != INT_MIN)
+			P_PoisonMobj(RailHits[i].HitActor, thepuff ? thepuff : source, source, puffDefaults->PoisonDamage, puffDefaults->PoisonDuration, puffDefaults->PoisonPeriod);
+
 		P_DamageMobj (RailHits[i].HitActor, thepuff? thepuff:source, source, damage, damagetype, DMG_INFLICTOR_IS_PUFF);
 	}
 
diff --git a/src/p_mobj.cpp b/src/p_mobj.cpp
index 6fd05c040..9c1e195ee 100644
--- a/src/p_mobj.cpp
+++ b/src/p_mobj.cpp
@@ -346,6 +346,11 @@ void AActor::Serialize (FArchive &arc)
 			WeaveIndexZ = 0;
 		}
 	}
+	if (SaveVersion >= 2450)
+	{
+		arc << PoisonDamageReceived << PoisonDurationReceived << PoisonPeriodReceived << Poisoner;
+		arc << PoisonDamage << PoisonDuration << PoisonPeriod;
+	}
 
 	// Skip past uservar array in old savegames
 	if (SaveVersion < 1933)
@@ -3314,6 +3319,18 @@ void AActor::Tick ()
 		{
 			return;
 		}
+
+		// Check for poison damage, but only once per PoisonPeriod tics (or once per second if none).
+		if (PoisonDurationReceived && (level.time % (PoisonPeriodReceived ? PoisonPeriodReceived : TICRATE) == 0))
+		{
+			P_DamageMobj(this, NULL, Poisoner, PoisonDamageReceived, NAME_Poison, 0);
+
+			--PoisonDurationReceived;
+
+			// Must clear damage when duration is done, otherwise it
+			// could be added to with ADDITIVEPOISONDAMAGE.
+			if (!PoisonDurationReceived) PoisonDamageReceived = 0;
+		}
 	}
 
 	// cycle through states, calling action functions at transitions
@@ -5444,10 +5461,10 @@ int AActor::DoSpecialDamage (AActor *target, int damage)
 	{
 		if (target->player)
 		{
-			int poisondamage = GetClass()->Meta.GetMetaInt(AMETA_PoisonDamage);
-			if (poisondamage > 0)
+			// Only do this for old style poison damage.
+			if (PoisonDamage > 0 && PoisonDuration == INT_MIN)
 			{
-				P_PoisonPlayer (target->player, this, this->target, poisondamage);
+				P_PoisonPlayer (target->player, this, this->target, PoisonDamage);
 				damage >>= 1;
 			}
 		}
diff --git a/src/thingdef/thingdef_data.cpp b/src/thingdef/thingdef_data.cpp
index 7ebb680d8..b08e48719 100644
--- a/src/thingdef/thingdef_data.cpp
+++ b/src/thingdef/thingdef_data.cpp
@@ -224,6 +224,8 @@ static FFlagDef ActorFlags[]=
 	DEFINE_FLAG(MF6, JUMPDOWN, AActor, flags6),
 	DEFINE_FLAG(MF6, VULNERABLE, AActor, flags6),
 	DEFINE_FLAG(MF6, NOTRIGGER, AActor, flags6),
+	DEFINE_FLAG(MF6, ADDITIVEPOISONDAMAGE, AActor, flags6),
+	DEFINE_FLAG(MF6, ADDITIVEPOISONDURATION, AActor, flags6),
 	DEFINE_FLAG(MF6, BLOCKEDBYSOLIDACTORS, AActor, flags6),
 
 	// Effect flags
diff --git a/src/thingdef/thingdef_properties.cpp b/src/thingdef/thingdef_properties.cpp
index 0452cb951..ffe287035 100644
--- a/src/thingdef/thingdef_properties.cpp
+++ b/src/thingdef/thingdef_properties.cpp
@@ -999,10 +999,26 @@ DEFINE_PROPERTY(maxdropoffheight, F, Actor)
 //==========================================================================
 //
 //==========================================================================
-DEFINE_PROPERTY(poisondamage, I, Actor)
+DEFINE_PROPERTY(poisondamage, Iii, Actor)
 {
-	PROP_INT_PARM(i, 0);
-	info->Class->Meta.SetMetaInt (AMETA_PoisonDamage, i);
+	PROP_INT_PARM(poisondamage, 0);
+	PROP_INT_PARM(poisonduration, 1);
+	PROP_INT_PARM(poisonperiod, 2);
+
+	defaults->PoisonDamage = poisondamage;
+	if (PROP_PARM_COUNT == 1)
+	{
+		defaults->PoisonDuration = INT_MIN;
+	}
+	else
+	{
+		defaults->PoisonDuration = poisonduration;
+
+		if (PROP_PARM_COUNT > 2)
+			defaults->PoisonPeriod = poisonperiod;
+		else
+			defaults->PoisonPeriod = 0;
+	}
 }
 
 //==========================================================================