diff --git a/simulator.rkt b/simulator.rkt
index a9a3074..2ed89ad 100644
--- a/simulator.rkt
+++ b/simulator.rkt
@@ -208,10 +208,24 @@
 
           [(ApplyPrimitiveProcedure? op)
            m]
+          
           [(LookupLexicalAddress? op)
-           m]
+           (let: ([a-val : SlotValue (env-ref m (LookupLexicalAddress-depth op))])
+                 (cond
+                   [(toplevel? a-val)
+                    (error 'lookup-lexical-address)]
+                   [else
+                    (target-updater m a-val)]))]
+
           [(LookupToplevelAddress? op)
-           m]
+           (let: ([a-top : SlotValue (env-ref m (LookupToplevelAddress-depth op))])
+                 (cond
+                   [(toplevel? a-top)
+                    (target-updater m (list-ref (toplevel-vals a-top)
+                                                (LookupToplevelAddress-pos op)))]
+                   [else
+                    (error 'lookup-toplevel "not a toplevel: ~s" a-top)]))]
+         
           [(GetControlStackLabel? op)
            m])))
            
diff --git a/test-simulator.rkt b/test-simulator.rkt
index 0f63c47..cdea91d 100644
--- a/test-simulator.rkt
+++ b/test-simulator.rkt
@@ -373,9 +373,35 @@
                                              'moe))))
 
 
+;; Test toplevel lookup
+(let ([m (new-machine `(,(make-PerformStatement (make-ExtendEnvironment/Prefix! '(+)))
+                        ,(make-AssignPrimOpStatement 'val (make-LookupToplevelAddress 0 0 '+))))])
+  (test (machine-val (run m))
+        (lookup-primitive '+)))
+
+;; Test lexical lookup
+(let ([m (new-machine `(,(make-PerformStatement (make-ExtendEnvironment/Prefix! '(+)))
+                        ,(make-PushEnvironment 3)
+                        ,(make-AssignImmediateStatement (make-EnvLexicalReference 0) (make-Const 'larry))
+                        ,(make-AssignImmediateStatement (make-EnvLexicalReference 1) (make-Const 'curly))
+                        ,(make-AssignImmediateStatement (make-EnvLexicalReference 2) (make-Const 'moe))
+                        
+                        ,(make-AssignPrimOpStatement 'val (make-LookupLexicalAddress 0))))])
+  (test (machine-val (run m))
+        'larry))
+;; Another lexical lookup test
+(let ([m (new-machine `(,(make-PerformStatement (make-ExtendEnvironment/Prefix! '(+)))
+                        ,(make-PushEnvironment 3)
+                        ,(make-AssignImmediateStatement (make-EnvLexicalReference 0) (make-Const 'larry))
+                        ,(make-AssignImmediateStatement (make-EnvLexicalReference 1) (make-Const 'curly))
+                        ,(make-AssignImmediateStatement (make-EnvLexicalReference 2) (make-Const 'moe))
+                        
+                        ,(make-AssignPrimOpStatement 'val (make-LookupLexicalAddress 1))))])
+  (test (machine-val (run m))
+        'curly))
+
+
 
-#;(let ([m (new-machine `(,(make-AssignPrimOpStatement (make-ApplyPrimitiveProcedure))))])
-  (test ...))
 #;(let ([m (new-machine `(,(make-AssignPrimOpStatement (make-LookupLexicalAddress))))])
   (test ...))
 #;(let ([m (new-machine `(,(make-AssignPrimOpStatement (make-LookupToplevelAddress))))])