diff --git a/gc-notes.txt b/gc-notes.txt
index c36bbd08..98014d9c 100644
--- a/gc-notes.txt
+++ b/gc-notes.txt
@@ -12,6 +12,9 @@ TODO:
 
 - multiple mutators, and threading functions/types.  probably want this on a new branch, when ready
   part of this is implementing the beginnings of srfi-18, to create multiple threads, sync them, etc
+  TODO items:
+  - lock writes to symbol table
+
 - need to cooperate when a mutator is blocked
   might be able to stop a thread and do a minor GC on it, but no longjmp until after major GC.
   would need to figure out how to repack gc_cont and args
diff --git a/gc.c b/gc.c
index 2c0b7150..cc174ee8 100644
--- a/gc.c
+++ b/gc.c
@@ -1220,6 +1220,8 @@ void gc_thread_data_init(gc_thread_data *thd, int mut_num, char *stack_base, lon
   thd->stack_traces = calloc(MAX_STACK_TRACES, sizeof(char *));
   thd->stack_trace_idx = 0;
   thd->stack_prev_frame = NULL;
+//  thd->thread = NULL;
+  thd->thread_state = CYC_THREAD_STATE_NEW;
   //thd->mutator_num = mut_num;
   thd->jmp_start = malloc(sizeof(jmp_buf));
   thd->gc_args = malloc(sizeof(object) * NUM_GC_ANS);
diff --git a/include/cyclone/types.h b/include/cyclone/types.h
index 9ba3b8da..d88b557e 100644
--- a/include/cyclone/types.h
+++ b/include/cyclone/types.h
@@ -47,9 +47,18 @@
 /* Define general object type. */
 typedef void *object;
 
+/* Threading */
+typedef enum { CYC_THREAD_STATE_NEW
+             , CYC_THREAD_STATE_RUNNABLE
+             , CYC_THREAD_STATE_TERMINATED
+             } cyc_thread_state_type;
+
 /* Thread data structures */
 typedef struct gc_thread_data_t gc_thread_data;
 struct gc_thread_data_t {
+// TODO:
+//  pthread_t *thread;
+  cyc_thread_state_type thread_state;
   // Data needed to initiate stack-based minor GC
   char *stack_start;
   char *stack_limit;
diff --git a/runtime.c b/runtime.c
index d695abbe..578daba6 100644
--- a/runtime.c
+++ b/runtime.c
@@ -2491,6 +2491,9 @@ TODO: should rename this function to make it more clear what is really going on
  */
 void Cyc_start_thread(gc_thread_data *thd)
 {
+// TODO: should use an atomic set to modify this
+  thd->thread_state = CYC_THREAD_STATE_RUNNABLE;
+
   /* Tank, load the jump program... */
   setjmp(*(thd->jmp_start));
 
@@ -3141,6 +3144,9 @@ void *Cyc_init_thread(object thunk)
   thd->gc_cont = thunk;
   thd->gc_num_args = 1;
   thd->gc_args[0] = &Cyc_91end_91thread_67_primitive;
+//  thd->thread = pthread_self(); // TODO: ptr vs instance
+//  returns instance so would need to malloc here
+//  would also need to update termination code to free that memory
   gc_add_mutator(thd);
   Cyc_start_thread(thd);
   return NULL;
@@ -3193,6 +3199,8 @@ void Cyc_end_thread(gc_thread_data *thd)
   // referenced? might want to do one more minor GC to clear the stack before
   // terminating the thread
 
+// TODO: use ATOMIC set to modify this
+  thd->thread_state = CYC_THREAD_STATE_TERMINATED;
   pthread_exit(NULL); // For now, just a proof of concept
 }