diff --git a/cpu.js b/cpu.js
index d117a6a..9923010 100644
--- a/cpu.js
+++ b/cpu.js
@@ -79,7 +79,8 @@ function CPU_65816() {
                       0x98 : TYA, 0x4c : JMP_absolute, 
                       0x6c : JMP_absolute_indirect, 0x80 : BRA,
                       0xf0 : BEQ, 0xd0 : BNE, 0x90 : BCC, 0xb0 : BCS,
-                      0x50 : BVC, 0x70 : BVS, 0x10 : BPL, 0x30 : BMI };
+                      0x50 : BVC, 0x70 : BVS, 0x10 : BPL, 0x30 : BMI,
+                      0x69 : ADC_const };
 }
 
 var MMU = {
@@ -119,6 +120,44 @@ var MMU = {
   }
 };
 
+var ADC_const = {
+  bytes_required:function(cpu) {
+    if(cpu.p.m) {
+      return 2;
+    } else {
+      return 3;
+    }
+  },
+  execute:function(cpu, bytes) {
+    // TODO: Signed overflow checking.
+    if(cpu.p.m) {
+      cpu.r.a += bytes[0] + cpu.p.c;
+      if(cpu.r.a & 0x100) {
+        cpu.p.c = 1;
+      } else {
+        cpu.p.c = 0;
+      } 
+      cpu.r.a &= 0xff;
+      cpu.p.n = cpu.r.a >> 7;
+    } else {
+      cpu.r.a += (bytes[1]<<8)|bytes[0] + cpu.p.c;
+      if(cpu.r.a & 0x10000) {
+        cpu.p.c = 1;
+      } else {
+        cpu.p.c = 0; 
+      }
+      cpu.r.a &= 0xffff;
+      cpu.p.n = cpu.r.a >> 15;
+    }
+
+    if(cpu.r.a===0) {
+      cpu.p.z = 1;
+    } else {
+      cpu.p.z = 0;
+    }
+  }
+};
+
 var BMI = {
   bytes_required:function() {
     return 2;
diff --git a/test/tests.js b/test/tests.js
index f76a7a0..d85b42f 100644
--- a/test/tests.js
+++ b/test/tests.js
@@ -18,6 +18,66 @@ function run_tests() {
   test_rep();
   test_sep();
   test_branching();
+  test_adc();
+}
+
+function test_adc() {
+  module("ADC");
+  // TODO: signed overflow testing.
+  test("Test normal addition of two 16-bit numbers that don't cause an "+
+       "overflow (m bit is 0)", function() {
+     var cpu = new CPU_65816();
+     cpu.execute("18fb18c230a90100690100");
+     equals(cpu.r.a, 2, "0x0001 + 0x0001 should result in 0x0002 when using "+
+                        "ADC");
+     equals(cpu.p.n, 0, "0x0001 + 0x0001 does not result in a negative "+
+                        "two's complement number when adding with ADC."); 
+     equals(cpu.p.c, 0, "0x0001 + 0x0001 should not set the carry(c) bit when "+
+                        "adding with ADC");
+     equals(cpu.p.z, 0, "0x0001 + 0x0001 should not set the zero(z) bit when "+
+                        "adding with ADC");
+   });
+   test("Test normal addition of two 8-bit numbers that don't cause an "+
+       "overflow (m bit is 1)", function() {
+     var cpu = new CPU_65816();
+     cpu.execute("18fb18e230a9016901");
+     equals(cpu.r.a, 2, "0x01 + 0x01 should result in 0x02 when using "+
+                        "ADC");
+     equals(cpu.p.n, 0, "0x01 + 0x01 does not result in a negative "+
+                        "two's complement number when adding with ADC."); 
+     equals(cpu.p.c, 0, "0x01 + 0x01 should not set the carry(c) bit when "+
+                        "adding with ADC");
+     equals(cpu.p.z, 0, "0x01 + 0x01 should not set the zero(z) bit when "+
+                        "adding with ADC");
+   });
+  
+  test("Test that overflow sets the carry flag and works in general with two"+
+       "16-bit numbers (m bit is 0)", function() {
+    var cpu = new CPU_65816();
+    cpu.execute("18fb18c230a9ffff690100");
+    equals(cpu.p.c, 1, "0xffff + 0x0001 should set the carry bit when using "+
+                       "ADC");
+    equals(cpu.r.a, 0, "0xffff + 0x0001 should result in the accumulator "+
+                       "being 0 when using ADC");
+    equals(cpu.p.n, 0, "0xffff + 0x0001 should not set the negative(n) bit "+
+                       "when using ADC");
+    equals(cpu.p.z, 1, "0xffff + 0x0001 should set the zero(z) bit when using "+
+                       "ADC");
+  });
+
+  test("Test that overflow sets the carry flag and works in general with two"+
+       "8-bit numbers (m bit is 1)", function() {
+    var cpu = new CPU_65816();
+    cpu.execute("18fb18e230a9ff6901");
+    equals(cpu.p.c, 1, "0xff + 0x01 should set the carry bit when using "+
+                       "ADC");
+    equals(cpu.r.a, 0, "0xff + 0x01 should result in the accumulator "+
+                       "being 0 when using ADC");
+    equals(cpu.p.n, 0, "0xff + 0x01 should not set the negative(n) bit when "+
+                       "using ADC");
+    equals(cpu.p.z, 1, "0xff + 0x01 should set the zero(z) bit when using "+
+                       "ADC");
+  });
 }
 
 function test_branching() {