diff --git a/mps/code/event.c b/mps/code/event.c
index ca50a4ea32f..b97714f62b4 100644
--- a/mps/code/event.c
+++ b/mps/code/event.c
@@ -38,7 +38,7 @@ static Count eventUserCount;
 static Serial EventInternSerial;
 
 char *EventNext, *EventLimit; /* Used by macros in <code/event.h> */
-Word EventKindControl; /* Bit set used to control output. */
+EventControlSet EventKindControl; /* Bit set used to control output. */
 
 
 /* EventFlush -- flush event buffer to the event stream */
@@ -162,11 +162,14 @@ void EventFinish(void)
  *   Reset(M) EventControl(M,0)
  *   Flip(M)  EventControl(0,M)
  *   Read()   EventControl(0,0)
+ *
+ * FIXME: Candy-machine interface is a transgression.
  */
   
-Word EventControl(Word resetMask, Word flipMask)
+EventControlSet EventControl(EventControlSet resetMask,
+                             EventControlSet flipMask)
 {
-  Word oldValue = EventKindControl;
+  EventControlSet oldValue = EventKindControl;
      
   /* EventKindControl = (EventKindControl & ~resetMask) ^ flipMask */
   EventKindControl =
@@ -178,37 +181,33 @@ Word EventControl(Word resetMask, Word flipMask)
 
 /* EventInternString -- emit an Intern event on the (null-term) string given */
 
-Word EventInternString(const char *label)
+EventStringId EventInternString(const char *label)
 {
-  Word id;
-
   AVER(label != NULL);
-
-  id = (Word)EventInternSerial;
-  ++EventInternSerial;
-  EVENT2S(Intern, id, StringLength(label), label);
-  return id;
+  return EventInternGenString(StringLength(label), label);
 }
 
 
 /* EventInternGenString -- emit an Intern event on the string given */
 
-Word EventInternGenString(size_t len, const char *label)
+EventStringId EventInternGenString(size_t len, const char *label)
 {
-  Word id;
+  EventStringId id;
 
   AVER(label != NULL);
 
-  id = (Word)EventInternSerial;
+  id = EventInternSerial;
   ++EventInternSerial;
+
   EVENT2S(Intern, id, len, label);
+
   return id;
 }
 
 
 /* EventLabelAddr -- emit event to label address with the given id */
 
-void EventLabelAddr(Addr addr, Word id)
+void EventLabelAddr(Addr addr, EventStringId id)
 {
   AVER((Serial)id < EventInternSerial);
 
@@ -221,13 +220,13 @@ void EventLabelAddr(Addr addr, Word id)
 
 Res (EventSync)(void)
 {
-  return(ResOK); 
+  return ResOK;
 }
 
 
 Res (EventInit)(void)
 {
-  return(ResOK); 
+  return ResOK;
 }
 
 
@@ -237,28 +236,28 @@ void (EventFinish)(void)
 }
 
 
-Word (EventControl)(Word resetMask, Word flipMask)
+EventControlSet (EventControl)(EventControlSet resetMask,
+                               EventControlSet flipMask)
 {
   UNUSED(resetMask);
   UNUSED(flipMask);
-
-  return (Word)0;
+  return BS_EMPTY(EventControlSet);
 }
 
 
-Word (EventInternString)(const char *label)
+EventStringId (EventInternString)(const char *label)
 {
   UNUSED(label);
-
-  return (Word)0;
+  NOTREACHED;
+  return (EventInternString)0x9024EACH;
 }
 
 
 Word (EventInternGenString)(size_t len, const char *label)
 {
   UNUSED(len); UNUSED(label);
-
-  return (Word)0;
+  NOTREACHED;
+  return (EventInternString)0x9024EACH;
 }
 
 
@@ -266,6 +265,7 @@ void (EventLabelAddr)(Addr addr, Word id)
 {
   UNUSED(addr);
   UNUSED(id);
+  NOTREACHED;
 }
 
 
diff --git a/mps/code/event.h b/mps/code/event.h
index 161aa32d2e5..9af0225d7fd 100644
--- a/mps/code/event.h
+++ b/mps/code/event.h
@@ -20,13 +20,17 @@
 #include "eventdef.h"
 
 
+typedef Word EventStringId;
+typedef Word EventControlSet;
+
 extern Res EventSync(void);
 extern Res EventInit(void);
 extern void EventFinish(void);
-extern Word EventControl(Word, Word);
-extern Word EventInternString(const char *);
-extern Word EventInternGenString(size_t, const char *);
-extern void EventLabelAddr(Addr, Word);
+extern EventControlSet EventControl(EventControlSet resetMask,
+                                    EventControlSet flipMask);
+extern EventStringId EventInternString(const char *label);
+extern EventStringId EventInternGenString(size_t, const char *label);
+extern void EventLabelAddr(Addr addr, Word id);
 extern Res EventFlush(void);
 
 
@@ -38,10 +42,13 @@ extern char *EventNext, *EventLimit;
 extern Word EventKindControl;
 
 
+/* TODO: Append a size at EventNext - sizeof(EventSize) so that a backtrace
+   can step backwards through the event buffer. */
+
 #define EVENT_BEGIN(name, structSize) \
   BEGIN \
-    if(Event##name##Always && \
-       BS_IS_MEMBER(EventKindControl, ((Index)Event##name##Kind))) { \
+    if(/* Event##name##Always && FIXME: depend on variety */ \
+       BS_IS_MEMBER(EventKindControl, (Index)Event##name##Kind)) { \
       Event##name##Struct *_event; \
       size_t _size = size_tAlignUp(structSize, MPS_PF_ALIGN); \
       if (_size > (size_t)(EventLimit - EventNext)) \
@@ -103,14 +110,6 @@ extern Word EventKindControl;
 #else /* EVENT not */
 
 
-#define EventInit()            NOOP
-#define EventFinish()          NOOP
-#define EventControl(r, f)     (UNUSED(r), UNUSED(f), (Word)0)
-#define EventInternString(s)   (UNUSED(s), (Word)0)
-#define EventInternGenString(l, s) (UNUSED(l), UNUSED(s), (Word)0)
-#define EventLabelAddr(a, i)   BEGIN UNUSED(a); UNUSED(i); END
-
-
 #define EVENT0(name) NOOP
 /* The following lines were generated with
   python -c 'for i in range(1,15): print "#define EVENT%d(name, %s) NOOP" % (i, ", ".join(["p%d" % j for j in range(0, i)]))'