diff --git a/include/cyclone/runtime-main.h b/include/cyclone/runtime-main.h
index da75c5b4..a68c721b 100644
--- a/include/cyclone/runtime-main.h
+++ b/include/cyclone/runtime-main.h
@@ -23,25 +23,6 @@ static void Cyc_main (stack_size,heap_size,stack_base)
  mclosure0(clos_halt,&Cyc_halt);  /* Halt program if final closure is reached */
  gc_ans[0] = &clos_halt;
  gc_num_ans = 1;
- /* Allocate stack buffer. */
- stack_begin = stack_base;
-#if STACK_GROWS_DOWNWARD
- stack_limit1 = stack_begin - stack_size;
- stack_limit2 = stack_limit1 - 2000;
-#else
- stack_limit1 = stack_begin + stack_size;
- stack_limit2 = stack_limit1 + 2000;
-#endif
-#if DEBUG_SHOW_DIAG
- printf("main: sizeof(cons_type)=%ld\n",(long) sizeof(cons_type));
-#endif
- if (check_overflow(stack_base,&in_my_frame))
-   {printf("main: Recompile with STACK_GROWS_DOWNWARD set to %ld\n",
-           (long) (1-STACK_GROWS_DOWNWARD)); exit(0);}
-#if DEBUG_SHOW_DIAG
- printf("main: stack_size=%ld  stack_base=%p  stack_limit1=%p\n",
-        stack_size,(void *)stack_base,(void *)stack_limit1);
-#endif
 
  /* Initialize stack trace table */
  Cyc_st_init();
@@ -58,7 +39,6 @@ static void Cyc_main (stack_size,heap_size,stack_base)
 #endif
 
   Cyc_heap = gc_heap_create(heap_size / 2, 0, 0);
-  //Cyc_heap = gc_heap_create(1024, 0, 0);
   Cyc_thread = malloc(sizeof(gc_thread_data));
   gc_thread_data_init(Cyc_thread, stack_base, stack_size);
   
diff --git a/include/cyclone/runtime.h b/include/cyclone/runtime.h
index b531e1d4..63b98f1b 100644
--- a/include/cyclone/runtime.h
+++ b/include/cyclone/runtime.h
@@ -210,9 +210,6 @@ void do_dispatch(void *data, int argc, function_type func, object clo, object *b
 extern gc_heap *Cyc_heap;
 extern gc_thread_data *Cyc_thread;
 extern clock_t start;   /* Starting time. */
-extern char *stack_begin;   /* Initialized by main. */
-extern char *stack_limit1;  /* Initialized by main. */
-extern char *stack_limit2;
 extern char *bottom;    /* Bottom of tospace. */
 extern char *allocp;    /* Cheney allocate pointer. */
 extern char *alloc_end;
diff --git a/runtime.c b/runtime.c
index 7b815a40..2f9f75e7 100644
--- a/runtime.c
+++ b/runtime.c
@@ -64,7 +64,7 @@ void Cyc_check_bounds(void *data, const char *label, int len, int index) {
 /* Return to continuation after checking for stack overflow. */
 #define return_closcall1(td,cfn,a1) \
 {char stack; \
- if (check_overflow(&stack,stack_limit1)) { \
+ if (check_overflow(&stack,(((gc_thread_data *)data)->stack_limit))) { \
      object buf[1]; buf[0] = a1;\
      GC(td,cfn,buf,1); return; \
  } else {closcall1(td,(closure) (cfn),a1); return;}}
@@ -72,7 +72,7 @@ void Cyc_check_bounds(void *data, const char *label, int len, int index) {
 /* Return to continuation after checking for stack overflow. */
 #define return_closcall2(td,cfn,a1,a2) \
 {char stack; \
- if (check_overflow(&stack,stack_limit1)) { \
+ if (check_overflow(&stack,(((gc_thread_data *)data)->stack_limit))) { \
      object buf[2]; buf[0] = a1;buf[1] = a2;\
      GC(td,cfn,buf,2); return; \
  } else {closcall2(td,(closure) (cfn),a1,a2); return;}}
@@ -82,9 +82,6 @@ void Cyc_check_bounds(void *data, const char *label, int len, int index) {
 gc_heap *Cyc_heap;
 gc_thread_data *Cyc_thread;
 clock_t start;   /* Starting time. */
-char *stack_begin;   /* Initialized by main. */
-char *stack_limit1;  /* Initialized by main. */
-char *stack_limit2;
 char *bottom;    /* Bottom of tospace. */
 char *allocp;    /* Cheney allocate pointer. */
 char *alloc_end;
@@ -2603,7 +2600,7 @@ void GC(void *data, closure cont, object *args, int num_args)
   char tmp;
   object temp;
   object low_limit = &tmp; // This is one end of the stack...
-  object high_limit = stack_begin; // TODO: move to thread-specific struct
+  object high_limit = ((gc_thread_data *)data)->stack_start;
   int i;
   int scani = 0, alloci = 0; // TODO: not quite sure how to do this yet, want to user pointers but realloc can move them... need to think about how this will work
   int heap_grown = 0;
diff --git a/scheme/cyclone/cgen.sld b/scheme/cyclone/cgen.sld
index c326cda1..4fcc5ba3 100644
--- a/scheme/cyclone/cgen.sld
+++ b/scheme/cyclone/cgen.sld
@@ -112,7 +112,7 @@
       "/* Check for GC, then call given continuation closure */\n"
       "#define return_closcall" n "(td,cfn" args ") \\\n"
       "{char stack; \\\n"
-      " if (check_overflow(&stack,stack_limit1)) { \\\n"
+      " if (check_overflow(&stack,(((gc_thread_data *)data)->stack_limit))) { \\\n"
       "     object buf[" n "]; " arry-assign "\\\n"
       "     GC(td,cfn,buf," n "); return; \\\n"
       " } else {closcall" n "(td,(closure) (cfn)" args "); return;}}\n")))
@@ -125,7 +125,7 @@
       "/* Check for GC, then call C function directly */\n"
       "#define return_direct" n "(td,_fn" args ") { \\\n"
       " char stack; \\\n"
-      " if (check_overflow(&stack,stack_limit1)) { \\\n"
+      " if (check_overflow(&stack,(((gc_thread_data *)data)->stack_limit))) { \\\n"
       "     object buf[" n "]; " arry-assign " \\\n"
       "     mclosure0(c1, _fn); \\\n"
       "     GC(td,&c1, buf, " n "); return; \\\n"