diff --git a/sample/sample.js b/sample/sample.js
index 5bd9c00..1098009 100644
--- a/sample/sample.js
+++ b/sample/sample.js
@@ -20,7 +20,8 @@ let p = new Parser();
 let sl = p.parse(prog);
 let asm = new Assembler();
 asm.setTracing(true);
-let mem = asm.assemble(sl);
+let [mem, labelToAddr] = asm.assemble(sl);
+console.log(labelToAddr);
 
 // Set up memory access functions for the simulator.
 function memoryTo(addr, value) {
diff --git a/src/assembler.js b/src/assembler.js
index 1221eb7..ccb281f 100644
--- a/src/assembler.js
+++ b/src/assembler.js
@@ -31,7 +31,7 @@ class Assembler {
   assemble(sourceLines) {
     this._assembleInstructions(sourceLines);
     this._applyFixups();
-    return this.memory;
+    return [this.memory, this.labelToAddr];
   }
 
   // Set tracing mode: true or false;
diff --git a/test/test.js b/test/test.js
index 50aa294..d5efd4b 100644
--- a/test/test.js
+++ b/test/test.js
@@ -16,7 +16,7 @@ function runProg(progText, maxSteps) {
   let p = new Parser();
   let asm = new Assembler();
   let sourceLines = p.parse(progText);
-  let mem = asm.assemble(sourceLines);
+  let [mem, labelToAddr] = asm.assemble(sourceLines);
 
   const memoryTo = (addr, value) => {mem[addr] = value;};
   const memoryAt = (addr) => {return mem[addr];};
@@ -35,7 +35,7 @@ function runProg(progText, maxSteps) {
     }
   }
 
-  return [CPU8080.status(), mem];
+  return [CPU8080.status(), mem, labelToAddr];
 }
 
 describe('sim', () => {
@@ -121,6 +121,29 @@ describe('sim', () => {
     assert.equal(state.a, 100);
   });
 
+  it('labels-to-addr', () => {
+    // Verifies that labels have been mapped onto addresses as expected.
+    let [state, mem, labelToAddr] = runProg(`
+    Start:
+          mvi a, 50       ; 2 bytes each
+          mvi b, 20
+          mvi c, 100
+          jmp Uno         ; 3 bytes
+    Tres: add b           ; 1 bytes for add/hlt each
+          hlt
+    Uno:  jmp Dos
+          add c
+    Dos:  jmp Tres
+          add c
+    `);
+    assert.ok(state.halted);
+
+    assert.equal(labelToAddr.get('Start'), 0);
+    assert.equal(labelToAddr.get('Tres'), 9);
+    assert.equal(labelToAddr.get('Uno'), 11);
+    assert.equal(labelToAddr.get('Dos'), 15);
+  });
+
   it('chainjmp', () => {
     let [state, mem] = runProg(`
           mvi a, 50