diff --git a/Sources/Engine/Base/Anim.cpp b/Sources/Engine/Base/Anim.cpp
index e491e12..10d04e8 100644
--- a/Sources/Engine/Base/Anim.cpp
+++ b/Sources/Engine/Base/Anim.cpp
@@ -173,16 +173,14 @@ BOOL CAnimData::IsAutoFreed(void)
 // Reference counting functions
 void CAnimData::AddReference(void)
 {
-  if (this!=NULL) {
-    MarkUsed();
-  }
+  ASSERT(this!=NULL);
+  MarkUsed();
 }
 
 void CAnimData::RemReference(void)
 {
-  if (this!=NULL) {
-    RemReference_internal();
-  }
+  ASSERT(this!=NULL);
+  RemReference_internal();
 }
 
 void CAnimData::RemReference_internal(void)
diff --git a/Sources/Engine/Base/Console.cpp b/Sources/Engine/Base/Console.cpp
index 208fa49..a8d613a 100644
--- a/Sources/Engine/Base/Console.cpp
+++ b/Sources/Engine/Base/Console.cpp
@@ -44,9 +44,7 @@ CConsole::CConsole(void)
 // Destructor.
 CConsole::~CConsole(void)
 {
-  if (this==NULL) {
-    return;
-  }
+  ASSERT(this!=NULL);
   if (con_fLog!=NULL) {
     fclose(con_fLog);
     con_fLog = NULL;
@@ -102,25 +100,19 @@ void CConsole::Initialize(const CTFileName &fnmLog, INDEX ctCharsPerLine, INDEX
 // Get current console buffer.
 const char *CConsole::GetBuffer(void)
 {
-  if (this==NULL) {
-    return "";
-  }
+  ASSERT(this!=NULL);
   return con_strBuffer+(con_ctLines-con_ctLinesPrinted)*(con_ctCharsPerLine+1);
 }
 INDEX CConsole::GetBufferSize(void)
 {
-  if (this==NULL) {
-    return 1;
-  }
+  ASSERT(this!=NULL);
   return (con_ctCharsPerLine+1)*con_ctLines+1;
 }
 
 // Discard timing info for last lines
 void CConsole::DiscardLastLineTimes(void)
 {
-  if (this==NULL) {
-    return;
-  }
+  ASSERT(this!=NULL);
   for(INDEX i=0; i<con_ctLines; i++) {
     con_atmLines[i] = -10000.0f;
   }
@@ -129,9 +121,7 @@ void CConsole::DiscardLastLineTimes(void)
 // Get number of lines newer than given time
 INDEX CConsole::NumberOfLinesAfter(TIME tmLast)
 {
-  if (this==NULL) {
-    return 0;
-  }
+  ASSERT(this!=NULL);
   // clamp console variable
   con_iLastLines = Clamp( con_iLastLines, 0, (INDEX)CONSOLE_MAXLASTLINES);
   // find number of last console lines to be displayed on screen
@@ -146,9 +136,7 @@ INDEX CConsole::NumberOfLinesAfter(TIME tmLast)
 // Get one of last lines
 CTString CConsole::GetLastLine(INDEX iLine)
 {
-  if (this==NULL) {
-    return "";
-  }
+  ASSERT(this!=NULL);
   if (iLine>=con_ctLinesPrinted) {
     return "";
   }
@@ -166,9 +154,7 @@ CTString CConsole::GetLastLine(INDEX iLine)
 // clear one given line in buffer
 void CConsole::ClearLine(INDEX iLine)
 {
-  if (this==NULL) {
-    return;
-  }
+  ASSERT(this!=NULL);
   // line must be valid
   ASSERT(iLine>=0 && iLine<con_ctLines);
   // get start of line
@@ -183,9 +169,7 @@ void CConsole::ClearLine(INDEX iLine)
 // scroll buffer up, discarding lines at the start
 void CConsole::ScrollBufferUp(INDEX ctLines)
 {
-  if (this==NULL) {
-    return;
-  }
+  ASSERT(this!=NULL);
   ASSERT(ctLines>0 && ctLines<con_ctLines);
   // move buffer up
   memmove(
@@ -207,9 +191,7 @@ void CConsole::ScrollBufferUp(INDEX ctLines)
 // Add a line of text to console
 void CConsole::PutString(const char *strString)
 {
-  if (this==NULL) {
-    return;
-  }
+  ASSERT(this!=NULL);
   // synchronize access to console
   CTSingleLock slConsole(&con_csConsole, TRUE);
 
@@ -265,9 +247,7 @@ void CConsole::PutString(const char *strString)
 // Close console log file buffers (call only when force-exiting!)
 void CConsole::CloseLog(void)
 {
-  if (this==NULL) {
-    return;
-  }
+  ASSERT(this!=NULL);
   if (con_fLog!=NULL) {
     fclose(con_fLog);
   }
diff --git a/Sources/Engine/Entities/Entity.cpp b/Sources/Engine/Entities/Entity.cpp
index de3acfe..89bf604 100644
--- a/Sources/Engine/Entities/Entity.cpp
+++ b/Sources/Engine/Entities/Entity.cpp
@@ -2036,10 +2036,7 @@ static CStaticStackArray<CSentEvent> _aseSentEvents;  // delayed events
 /* Send an event to this entity. */
 void CEntity::SendEvent(const CEntityEvent &ee)
 {
-  if (this==NULL) {
-    ASSERT(FALSE);
-    return;
-  }
+  ASSERT(this!=NULL);
   CSentEvent &se = _aseSentEvents.Push();
   se.se_penEntity = this;
   se.se_peeEvent = ((CEntityEvent&)ee).MakeCopy();  // discard const qualifier
diff --git a/Sources/Engine/Entities/Entity.h b/Sources/Engine/Entities/Entity.h
index b2bd944..5f98d38 100644
--- a/Sources/Engine/Entities/Entity.h
+++ b/Sources/Engine/Entities/Entity.h
@@ -694,18 +694,16 @@ inline CEntity& CEntityPointer::operator*(void) const { return *ep_pen; }
 /////////////////////////////////////////////////////////////////////
 // Reference counting functions
 inline void CEntity::AddReference(void) { 
-  if (this!=NULL) {
-    ASSERT(en_ctReferences>=0);
-    en_ctReferences++; 
-  }
+  ASSERT(this!=NULL);
+  ASSERT(en_ctReferences>=0);
+  en_ctReferences++; 
 };
 inline void CEntity::RemReference(void) { 
-  if (this!=NULL) {
-    ASSERT(en_ctReferences>0);
-    en_ctReferences--;
-    if(en_ctReferences==0) {
-      delete this;
-    }
+  ASSERT(this!=NULL);
+  ASSERT(en_ctReferences>0);
+  en_ctReferences--;
+  if(en_ctReferences==0) {
+    delete this;
   }
 };
 
diff --git a/Sources/Engine/Entities/EntityClass.cpp b/Sources/Engine/Entities/EntityClass.cpp
index a0e6163..1fb1881 100644
--- a/Sources/Engine/Entities/EntityClass.cpp
+++ b/Sources/Engine/Entities/EntityClass.cpp
@@ -64,14 +64,12 @@ CEntityClass::~CEntityClass(void)
 /////////////////////////////////////////////////////////////////////
 // Reference counting functions
 void CEntityClass::AddReference(void) {
-  if (this!=NULL) {
-    MarkUsed();
-  }
+  ASSERT(this!=NULL);
+  MarkUsed();
 };
 void CEntityClass::RemReference(void) {
-  if (this!=NULL) {
-    _pEntityClassStock->Release(this);
-  }
+  ASSERT(this!=NULL);
+  _pEntityClassStock->Release(this);
 };
 
 /*
diff --git a/Sources/Engine/Network/Network.cpp b/Sources/Engine/Network/Network.cpp
index e6e2b43..d283a1a 100644
--- a/Sources/Engine/Network/Network.cpp
+++ b/Sources/Engine/Network/Network.cpp
@@ -655,7 +655,8 @@ extern void FreeUnusedStock(void)
  */
 void CNetworkTimerHandler::HandleTimer(void)
 {
-  if (this==NULL || _bTempNetwork) {
+  ASSERT(this!=NULL);
+  if (_bTempNetwork) {
     return; // this can happen during NET_MakeDefaultState_t()!
   }
   // enable stream handling during timer
@@ -902,7 +903,8 @@ void CNetworkLibrary::Init(const CTString &strGameID)
  */
 void CNetworkLibrary::AddTimerHandler(void)
 {
-  if (this==NULL || _bTempNetwork) {
+  ASSERT(this!=NULL);
+  if (_bTempNetwork) {
     return; // this can happen during NET_MakeDefaultState_t()!
   }
   _pTimer->AddHandler(&ga_thTimerHandler);
@@ -912,7 +914,8 @@ void CNetworkLibrary::AddTimerHandler(void)
  */
 void CNetworkLibrary::RemoveTimerHandler(void)
 {
-  if (this==NULL || _bTempNetwork) {
+  ASSERT(this!=NULL);
+  if (_bTempNetwork) {
     return; // this can happen during NET_MakeDefaultState_t()!
   }
   _pTimer->RemHandler(&ga_thTimerHandler);
@@ -1390,7 +1393,8 @@ void CNetworkLibrary::TogglePause(void)
 // test if game is paused
 BOOL CNetworkLibrary::IsPaused(void)
 {
-  if (this==NULL || _bTempNetwork) {
+  ASSERT(this!=NULL);
+  if (_bTempNetwork) {
     return TRUE; // this can happen during NET_MakeDefaultState_t()!
   }
   return ga_sesSessionState.ses_bPause;
@@ -1427,7 +1431,8 @@ void CNetworkLibrary::SetLocalPause(BOOL bPause)
 
 BOOL CNetworkLibrary::GetLocalPause(void)
 {
-  if (this==NULL || _bTempNetwork) {
+  ASSERT(this!=NULL);
+  if (_bTempNetwork) {
     return TRUE; // this can happen during NET_MakeDefaultState_t()!
   }
   return ga_bLocalPause;
@@ -2033,7 +2038,8 @@ void CNetworkLibrary::SendActionsToServer(void)
  */
 void CNetworkLibrary::TimerLoop(void)
 {
-  if (this==NULL || _bTempNetwork) {
+  ASSERT(this!=NULL);
+  if (_bTempNetwork) {
     return; // this can happen during NET_MakeDefaultState_t()!
   }
   _pfNetworkProfile.StartTimer(CNetworkProfile::PTI_TIMERLOOP);
diff --git a/Sources/Engine/Sound/SoundData.cpp b/Sources/Engine/Sound/SoundData.cpp
index f022ebb..c9852c4 100644
--- a/Sources/Engine/Sound/SoundData.cpp
+++ b/Sources/Engine/Sound/SoundData.cpp
@@ -252,16 +252,14 @@ SLONG CSoundData::GetUsedMemory(void)
 // Add one reference
 void CSoundData::AddReference(void)
 {
-  if (this!=NULL) {
-    MarkUsed();
-  }
+  ASSERT(this!=NULL);
+  MarkUsed();
 }
 
 
 // Remove one reference
 void CSoundData::RemReference(void)
 {
-  if (this!=NULL) {
-    _pSoundStock->Release(this);
-  }
+  ASSERT(this!=NULL);
+  _pSoundStock->Release(this);
 }
diff --git a/Sources/Engine/Sound/SoundLibrary.cpp b/Sources/Engine/Sound/SoundLibrary.cpp
index f1e4df3..8bf8133 100644
--- a/Sources/Engine/Sound/SoundLibrary.cpp
+++ b/Sources/Engine/Sound/SoundLibrary.cpp
@@ -1233,6 +1233,7 @@ BOOL CSoundLibrary::SetEnvironment( INDEX iEnvNo, FLOAT fEnvSize/*=0*/)
 // mute all sounds (erase playing buffer(s) and supress mixer)
 void CSoundLibrary::Mute(void)
 {
+  ASSERT(this!=NULL);
   // stop all IFeel effects
   IFeel_StopEffect(NULL);
 
@@ -1244,7 +1245,7 @@ void CSoundLibrary::Mute(void)
 
 #ifdef PLATFORM_WIN32
   // erase direct sound buffer (waveout will shut-up by itself), but skip if there's no more sound library
-  if( this==NULL || !sl_bUsingDirectSound) return;
+  if(!sl_bUsingDirectSound) return;
 
   // synchronize access to sounds
   CTSingleLock slSounds(&sl_csSound, TRUE);
diff --git a/Sources/Engine/World/World.cpp b/Sources/Engine/World/World.cpp
index bff7b76..405904c 100644
--- a/Sources/Engine/World/World.cpp
+++ b/Sources/Engine/World/World.cpp
@@ -936,10 +936,11 @@ void CWorld::TriangularizeForVertices( CBrushVertexSelection &selVertex)
 // add this entity to prediction
 void CEntity::AddToPrediction(void)
 {
-  // this function may be called even for NULLs - so ignore it
-  if (this==NULL) {
-    return;
-  }
+  // this function may be called even for NULLs - TODO: fix those cases
+  //   (The compiler is free to assume that "this" is never NULL and optimize
+  //   based on that assumption. For example, an "if (this==NULL) {...}" could
+  //   be optimized away completely.)
+  ASSERT(this!=NULL);
   // if already added
   if (en_ulFlags&ENF_WILLBEPREDICTED) {
     // do nothing
diff --git a/Sources/Entities/Common/PathFinding.cpp b/Sources/Entities/Common/PathFinding.cpp
index e4099b2..91742a6 100644
--- a/Sources/Entities/Common/PathFinding.cpp
+++ b/Sources/Entities/Common/PathFinding.cpp
@@ -35,8 +35,9 @@ CPathNode::~CPathNode(void)
 // get name of this node
 const CTString &CPathNode::GetName(void)
 {
+  ASSERT(this!=NULL);
   static CTString strNone="<none>";
-  if (this==NULL || pn_pnmMarker==NULL) {
+  if (pn_pnmMarker==NULL) {
     return strNone;
   } else {
     return pn_pnmMarker->GetName();
@@ -46,7 +47,8 @@ const CTString &CPathNode::GetName(void)
 // get link with given index or null if no more (for iteration along the graph)
 CPathNode *CPathNode::GetLink(INDEX i)
 {
-  if (this==NULL || pn_pnmMarker==NULL) {
+  ASSERT(this!=NULL);
+  if (pn_pnmMarker==NULL) {
     ASSERT(FALSE);
     return NULL;
   }
diff --git a/Sources/EntitiesMP/Common/PathFinding.cpp b/Sources/EntitiesMP/Common/PathFinding.cpp
index 54a68f0..3504155 100644
--- a/Sources/EntitiesMP/Common/PathFinding.cpp
+++ b/Sources/EntitiesMP/Common/PathFinding.cpp
@@ -50,8 +50,9 @@ CPathNode::~CPathNode(void)
 // get name of this node
 const CTString &CPathNode::GetName(void)
 {
+  ASSERT(this!=NULL);
   static CTString strNone="<none>";
-  if (this==NULL || pn_pnmMarker==NULL) {
+  if (pn_pnmMarker==NULL) {
     return strNone;
   } else {
     return pn_pnmMarker->GetName();
@@ -61,10 +62,7 @@ const CTString &CPathNode::GetName(void)
 // get link with given index or null if no more (for iteration along the graph)
 CPathNode *CPathNode::GetLink(INDEX i)
 {
-  if (this==NULL || pn_pnmMarker==NULL) {
-    ASSERT(FALSE);
-    return NULL;
-  }
+  ASSERT(this!=NULL && pn_pnmMarker!=NULL);
   CNavigationMarker *pnm = pn_pnmMarker->GetLink(i);
   if (pnm==NULL) {
     return NULL;
diff --git a/Sources/Modeler/DlgPgInfoAttachingPlacement.cpp b/Sources/Modeler/DlgPgInfoAttachingPlacement.cpp
index 3d9b0df..8fbd8a2 100644
--- a/Sources/Modeler/DlgPgInfoAttachingPlacement.cpp
+++ b/Sources/Modeler/DlgPgInfoAttachingPlacement.cpp
@@ -69,7 +69,7 @@ INDEX CDlgPgInfoAttachingPlacement::GetCurrentAttachingPlacement(void)
 void CDlgPgInfoAttachingPlacement::SetPlacementReferenceVertex(INDEX iCenter, INDEX iFront, INDEX iUp)
 {
   // patch for calling before page is refreshed
-  if(this == NULL) return;
+  ASSERT(this!=NULL);
   CModelerView *pModelerView = CModelerView::GetActiveView();
   if(pModelerView == NULL) return;
   CModelerDoc* pDoc = pModelerView->GetDocument();