diff --git a/bltin.c b/bltin.c
index c3060ca..87f0ca2 100644
--- a/bltin.c
+++ b/bltin.c
@@ -14,6 +14,7 @@ Object Lt	= (Object){.type=OBLTIN, .beg= "<"};
 Object Gt	= (Object){.type=OBLTIN, .beg= ">"};
 Object Ne	= (Object){.type=OBLTIN, .beg= "!="};
 Object Eq	= (Object){.type=OBLTIN, .beg= "=="};
+Object Not	= (Object){.type=OBLTIN, .beg= "not"};
 
 Object Comma= (Object){.type=OBLTIN, .beg=","};
 Object Bquote= (Object){.type=OBLTIN, .beg="`"};
@@ -44,6 +45,7 @@ extern Object* fncar(Object *, Object *);
 extern Object* fncdr(Object *, Object *);
 extern Object* fncons(Object *, Object *);
 extern Object* fneq(Object *, Object *);
+extern Object* fnnot(Object *, Object *);
 extern Object* fnif(Object *, Object *);
 extern Object* fnge(Object *env, Object *list);
 extern Object* fngt(Object *env, Object *list);
@@ -75,6 +77,7 @@ bltinlookup(Object *obj)
 		{&Cdr ,fncdr},
 		{&Cons ,fncons},
         {&Eq, fneq},
+        {&Not, fnnot},
         {&Ne, fnne},
         {&If, fnif},
         {&Ge, fnge},
diff --git a/dat.h b/dat.h
index 3eb6166..eed8344 100644
--- a/dat.h
+++ b/dat.h
@@ -69,6 +69,7 @@ extern Object Progn;
 extern Object Macro;
 extern Object Setq;
 extern Object Eq;
+extern Object Not;
 extern Object Ne;
 extern Object If;
 extern Object Ge;
diff --git a/eval.c b/eval.c
index 8de8a13..5e0a5ea 100644
--- a/eval.c
+++ b/eval.c
@@ -267,6 +267,14 @@ _newint(int n)
 	return newint(gc, 1);
 }
 
+Object*
+fnnot(Object *env, Object *list)
+{
+	if(list->type != OCELL || exprlen(list)!= 1)
+		error("Malformed not");
+	return _newint(list->car == &Nil);
+}
+
 Object*
 fneq(Object *env, Object *list)
 {
diff --git a/obj.c b/obj.c
index 82f04db..ce51c90 100644
--- a/obj.c
+++ b/obj.c
@@ -63,7 +63,7 @@ newsymbol(GC *gc, char *str, int len)
 		&Nil,  &Minus, &Plus, &Mul, &Mod, &Div, &Ge, &Le,
 		&Lt, &Gt, &Ne, &Lambda, &Car, &Cdr, &Quote, &Cons,
 		&Define, &Setq, &Eq, &If, &Macro, &Progn, &Bquote,
-		&Comma,
+		&Comma, &Not,
 	};
 	for(int i = 0; i < sizeof(syms)/sizeof(syms[0]); ++i){
 		Object *c = syms[i];