diff --git a/src/lisp/compiler.dasc b/src/lisp/compiler.dasc
index b47ecf2..b3cdb9a 100644
--- a/src/lisp/compiler.dasc
+++ b/src/lisp/compiler.dasc
@@ -35,8 +35,9 @@
 extern void _do_gc(unsigned int ebp, unsigned int esp);
 
 |.macro run_gc;
-| push esp;
+| mov eax, esp;
 | push ebp;
+| push eax;
 | mov eax, _do_gc;
 | call eax;
 |.endmacro;
@@ -296,6 +297,15 @@
 
 			local_free(local, i);
 		}
+		else if (symstreq(fsym, "gc"))
+		{
+			if (nargs)
+			{
+				err("gc takes no arguments");
+			}
+
+			| run_gc;
+		}
 		else
 		{
 			struct function *func =
@@ -325,7 +335,10 @@
 		struct variable *v = find_variable(local, (char *)(val ^ SYMBOL_TAG));
 
 		if (!v)
+		{
+			fprintf(stderr, "var: %s\n", (char *)(val ^ SYMBOL_TAG));
 			err("Variable unbound");
+		}
 
 		switch (v->type)
 		{
@@ -333,7 +346,7 @@
 			| mov eax, dword [ebp + (value_size * (v->number + 2))];
 			break;
 		case V_BOUND:
-			| mov eax, dword [ebp - ((v->number + 1) * value_size)]
+			| mov eax, dword [ebp - ((v->number + 1) * value_size)];
 			break;
 		default:
 			err("Sorry, can only access V_ARGUMENT and V_BOUND variables for now :(");
diff --git a/src/lisp/gc.c b/src/lisp/gc.c
index f3d01db..84df7aa 100644
--- a/src/lisp/gc.c
+++ b/src/lisp/gc.c
@@ -1,7 +1,9 @@
 #include "gc.h"
 #include "lisp.h"
+#include "plat/plat.h"
 
 value_t *gc_base;
+THREAD_LOCAL static unsigned int gc_mark;
 
 void __attribute__((noinline)) gc_set_base_here()
 {
@@ -11,17 +13,52 @@
 	asm("movl %%esp, %0" : "=g"(gc_base));
 }
 
-void _mark(value_t value)
+void _mark(value_t value, unsigned int *marked)
 {
 	if (heapp(value))
 	{
+		void *pointer = (void *)(value & ~HEAP_MASK);
+		struct alloc *alloc = pointer - sizeof(struct alloc);
 
+		fprintf(stderr, "[ GC ] Marking 0x%p\n", pointer);
+
+		// Only recursively mark if this hasn't been marked yet. i.e. prevent
+		// marking circular references twice
+		if (alloc->mark != gc_mark)
+		{
+			++*marked;
+
+			alloc->mark = gc_mark;
+
+			// printf("[ GC ] val =");
+			// printval(alloc_to_value(alloc), 2);
+
+			switch (alloc->type_tag)
+			{
+			case CONS_TAG: {
+				struct cons_alloc *cons = (struct cons_alloc *)alloc;
+				_mark(cons->cons.car, marked);
+				_mark(cons->cons.cdr, marked);
+				break;
+			}
+			}
+		}
 	}
 }
 
+value_t alloc_to_value(struct alloc *a)
+{
+	void *val = ((void *)a) + sizeof(struct alloc);
+	return (unsigned int)val | a->type_tag;
+}
+
 void _sweep()
 {
-
+	for (struct alloc *a = first_a; a; a = a->next)
+	{
+		fprintf(stderr, "[ GC ] %s %p\n", (a->mark != gc_mark) ? "Unmarked" : "Marked", a);
+		printval(alloc_to_value(a), 2);
+	}
 }
 
 void _do_gc(unsigned int esp, unsigned int ebp)
@@ -29,7 +66,11 @@
 	value_t *esp_p = (value_t *)esp,
 		*ebp_p = (value_t *)ebp;
 	
-	int num_marked = 0;
+	unsigned int num_marked = 0;
+
+	gc_mark++;
+
+	fprintf(stderr, "[ GC ] %d (esp 0x%p, ebp 0x%p)\n", gc_mark, esp_p, ebp_p);
 
 	// For every stack frame until the base of the stack
 	while (esp_p < gc_base)
@@ -39,8 +80,7 @@
 		// frame.
 		for (; esp_p < ebp_p && esp_p < gc_base; esp_p++)
 		{
-			_mark(*esp_p);
-			num_marked++;
+			_mark(*esp_p, &num_marked);
 		}
 
 		// Set the frame pointer to the frame pointer on the stack
@@ -52,4 +92,6 @@
 	}
 
 	fprintf(stderr, "Marked %d\n", num_marked);
+
+	_sweep();
 }
diff --git a/src/lisp/gc.h b/src/lisp/gc.h
index e535212..a75cadd 100644
--- a/src/lisp/gc.h
+++ b/src/lisp/gc.h
@@ -7,6 +7,7 @@
 
 void gc_set_base_here();
 
+value_t alloc_to_value(struct alloc *a);
 void _do_gc(unsigned int esp, unsigned int ebp);
-void _mark(unsigned int value);
+void _mark(value_t value, unsigned int *marked);
 void _sweep();
diff --git a/src/lisp/lisp.c b/src/lisp/lisp.c
index 50da78a..a015d4e 100644
--- a/src/lisp/lisp.c
+++ b/src/lisp/lisp.c
@@ -33,13 +33,14 @@
 	c->car = car;
 	c->cdr = cdr;
 
-	item->alloc.type_tag = T_CONS;
+	item->alloc.type_tag = CONS_TAG;
 
 	if (last_a)
 	{
 		item->alloc.prev = last_a;
 		last_a->next = item;
 		item->alloc.next = NULL;
+		last_a = item;
 	}
 	else
 	{
diff --git a/src/lisp/lisp.h b/src/lisp/lisp.h
index 1424abe..03ab75e 100644
--- a/src/lisp/lisp.h
+++ b/src/lisp/lisp.h
@@ -4,18 +4,6 @@
 #include <stdbool.h>
 #include <stdio.h>
 
-enum type
-{
-	T_INT = 0,
-	T_FLOAT,
-	T_NIL,
-	T_SYMBOL,
-	T_STRING,
-	T_VECTOR,
-	T_CLASS,
-	T_CONS,
-};
-
 #define INT_MASK 0b11
 #define INT_TAG 0b00
 
@@ -42,15 +30,20 @@
 	value_t car, cdr;
 };
 
+
+// It is integral that this be 16 bytes long so that whatever follows it is
+// still aligned to 4 bits.
 struct alloc
 {
-	unsigned int type_tag;
-	struct alloc *prev, *next;
-	unsigned int marked;
+	unsigned int type_tag;     //   4
+	struct alloc *prev, *next; // + 8
+	unsigned int mark;         // + 4 = 16
 
 	// Whatever else
 };
 
+extern struct alloc *first_a, *last_a;
+
 struct cons_alloc
 {
 	struct alloc alloc;
diff --git a/src/lisp/main.c b/src/lisp/main.c
index 8a50a5e..d0ddeef 100644
--- a/src/lisp/main.c
+++ b/src/lisp/main.c
@@ -1,11 +1,12 @@
 #include "compiler.h"
 #include "lisp.h"
+#include "gc.h"
 
 int main(int argc, char **argv)
 {
 	if (argc < 2)
 	{
-		puts("pass the string you want to parse as the first argument please");
+		puts("pass the program you want to run as the first argument please");
 		return 1;
 	}
 
@@ -17,7 +18,9 @@
 		return 1;
 	}
 
-	struct environment env = compile_all (is);
-	value_t (*lisp_main) () = find_function(&env, "main")->def0;
-	lisp_main ();
+	struct environment env = compile_all(is);
+	value_t (*lisp_main)() = find_function(&env, "main")->def0;
+
+	gc_set_base_here();
+	lisp_main();
 }
diff --git a/src/lisp/plat/plat.h b/src/lisp/plat/plat.h
index f10676c..3640005 100644
--- a/src/lisp/plat/plat.h
+++ b/src/lisp/plat/plat.h
@@ -12,3 +12,5 @@
 void free_aligned(void *addr);
 
 void *link(dasm_State **Dst);
+
+#define THREAD_LOCAL
diff --git a/src/lisp/test.lisp b/src/lisp/test.lisp
index a8ad05e..f51ef99 100644
--- a/src/lisp/test.lisp
+++ b/src/lisp/test.lisp
@@ -1,12 +1,15 @@
 (defun add-two (a)
   (+ a 2))
 
-(defun main-old ()
-  (if t
-    (print (add-two (* 4 3)))
-    (print (- 3 6))))
+(defun calls-gc (whatever)
+  (print whatever)
+  (gc))
 
 (defun main ()
-  (let1 (a 3)
+  (let1 (a (add-two 3))
     (print "a is")
-    (print a)))
+    (print a))
+  
+  (let1 (unused-but-bound (cons 5 6))
+    (let1 (val (cons 1 (cons 2 (cons 3 nil))))
+      (calls-gc val))))