diff --git a/gc.c b/gc.c
index 8be59a00..2d04fa83 100644
--- a/gc.c
+++ b/gc.c
@@ -694,100 +694,6 @@ PHASE 2 - multi-threaded mutator (IE, more than one stack thread):
 /////////////////////////////////////////////
 // GC functions called by the Mutator threads
 
-// Scan the given object and its refs, marking all heap objects. The issue
-// here is that the heap's write barrier can be invoked at any time and
-// we need to ensure any heap objects affected are traced
-void gc_stack_mark_gray3(gc_thread_data *thd, object obj, int depth)
-{
-  char tmp;
-  object low_limit = &tmp;
-  object high_limit = ((gc_thread_data *)thd)->stack_start;
-  int color;
-
-// TODO: is it just a coincidence that a corrupted lambda list element
-// was at 15? this approach may not work for deep lists, and may not
-// work at all. may need to replace with another method that is complete
-// but also handles circular references...
-  if (is_object_type(obj) && depth < 15) {
-    color = mark(obj);
-#if GC_SAFETY_CHECKS
-    if (check_overflow(low_limit, obj) && 
-        check_overflow(obj, high_limit) &&
-        color != gc_color_red){ 
-      fprintf(stderr, "stack object has wrong color %d!\n", color);
-      Cyc_display(obj, stderr);
-      fprintf(stderr, "\n");
-      exit(1);
-    }
-#endif
-    if (color == gc_color_clear) {
-      pthread_mutex_lock(&(thd->lock));
-      gc_mark_gray(thd, obj);
-      pthread_mutex_unlock(&(thd->lock));
-      //fprintf(stderr, "marked heap obj from stack barrier %p %d\n", obj, color);
-    } else if (color == gc_color_red) {
-      gc_stack_mark_refs_gray(thd, obj, depth + 1);
-    }
-  }
-}
-
-void gc_stack_mark_gray(gc_thread_data *thd, object obj)
-{
-  gc_stack_mark_gray3(thd, obj, 0);
-}
-
-// Should only be called from above function as a helper
-//
-// TODO: this will probably hang procssing circular
-// references!!!! need to extend this once the concept is proven
-//
-// ideally would need some way of recording which nodes have
-// been visited. trick is that, unlike in other places, the
-// nodes may be visited multiple times so cannot destructively
-// alter them.
-void gc_stack_mark_refs_gray(gc_thread_data *thd, object obj, int depth)
-{
-  switch(type_of(obj)) {
-    case cons_tag: {
-      gc_stack_mark_gray3(thd, car(obj), depth);
-      gc_stack_mark_gray3(thd, cdr(obj), depth);
-      break;
-    }
-    case closure1_tag:
-      gc_stack_mark_gray3(thd, ((closure1) obj)->elt1, depth);
-      break;
-    case closure2_tag:
-      gc_stack_mark_gray3(thd, ((closure2) obj)->elt1, depth);
-      gc_stack_mark_gray3(thd, ((closure2) obj)->elt2, depth);
-    case closure3_tag:
-      gc_stack_mark_gray3(thd, ((closure3) obj)->elt1, depth);
-      gc_stack_mark_gray3(thd, ((closure3) obj)->elt2, depth);
-      gc_stack_mark_gray3(thd, ((closure3) obj)->elt3, depth);
-    case closure4_tag:
-      gc_stack_mark_gray3(thd, ((closure4) obj)->elt1, depth);
-      gc_stack_mark_gray3(thd, ((closure4) obj)->elt2, depth);
-      gc_stack_mark_gray3(thd, ((closure4) obj)->elt3, depth);
-      gc_stack_mark_gray3(thd, ((closure4) obj)->elt4, depth);
-      break;
-    case closureN_tag: {
-      int i, n = ((closureN) obj)->num_elt;
-      for (i = 0; i < n; i++) {
-        gc_stack_mark_gray3(thd, ((closureN) obj)->elts[i], depth);
-      }
-      break;
-    }
-    case vector_tag: {
-      int i, n = ((vector) obj)->num_elt;
-      for (i = 0; i < n; i++) {
-        gc_stack_mark_gray3(thd, ((vector) obj)->elts[i], depth);
-      }
-      break;
-    }
-    default:
-    break;
-  }
-}
-
 /**
  * Determine if object lives on the thread's stack
  */
diff --git a/include/cyclone/types.h b/include/cyclone/types.h
index ab73bed9..e7f9c809 100644
--- a/include/cyclone/types.h
+++ b/include/cyclone/types.h
@@ -162,8 +162,6 @@ void gc_thread_data_free(gc_thread_data *thd);
 int gc_is_stack_obj(gc_thread_data *thd, object obj);
 void gc_mut_update(gc_thread_data *thd, object old_obj, object value);
 void gc_mut_cooperate(gc_thread_data *thd, int buf_len);
-void gc_stack_mark_refs_gray(gc_thread_data *thd, object obj, int depth);
-void gc_stack_mark_gray(gc_thread_data *thd, object obj);
 void gc_mark_gray(gc_thread_data *thd, object obj);
 void gc_mark_gray2(gc_thread_data *thd, object obj);
 void gc_collector_trace();