diff --git a/cpu.c b/cpu.c
index 05de0e7..564197d 100644
--- a/cpu.c
+++ b/cpu.c
@@ -223,10 +223,10 @@ int emulate_6502_op(State6502 * state) {
 	case BRK: state->running = 0;
 		state->flags.b = 1;
 		break; //BRK
-	case CLC: unimplemented_instruction(state); break;
-	case CLD: unimplemented_instruction(state); break;
-	case CLI: unimplemented_instruction(state); break;
-	case CLV: unimplemented_instruction(state); break;
+	case CLC: state->flags.c = 0; break;
+	case CLD: state->flags.d = 0; break;
+	case CLI: state->flags.i = 0; break;
+	case CLV: state->flags.v = 0; break;
 	case NOP: break; //NOP
 	case PHA: unimplemented_instruction(state); break;
 	case PLA: unimplemented_instruction(state); break;
@@ -238,9 +238,9 @@ int emulate_6502_op(State6502 * state) {
 		unimplemented_instruction(state); break;
 	case RTI: unimplemented_instruction(state); break;
 	case RTS: unimplemented_instruction(state); break;
-	case SEC: unimplemented_instruction(state); break;
-	case SED: unimplemented_instruction(state); break;
-	case SEI: unimplemented_instruction(state); break;
+	case SEC: state->flags.c = 1; break;
+	case SED: state->flags.d = 1; break;
+	case SEI: state->flags.i = 1; break;
 	case TAX: state->x = state->a; set_NZ_flags(state, state->x); break; //TODO test
 	case TXA: state->a = state->x; set_NZ_flags(state, state->a); break; //TODO test
 	case TAY: state->y = state->a; set_NZ_flags(state, state->y); break; //TODO test
diff --git a/test6502.c b/test6502.c
index 327bb45..0b686fe 100644
--- a/test6502.c
+++ b/test6502.c
@@ -97,6 +97,33 @@ void assert_flag_z(State6502 * state, byte expected) {
 	}
 }
 
+void assert_flag_c(State6502* state, byte expected) {
+	if (state->flags.c != expected) {
+		printf("Unexpected value in flag C, expected %d, was %d", expected, state->flags.c);
+		exit(1);
+	}
+}
+
+void assert_flag_i(State6502* state, byte expected) {
+	if (state->flags.i != expected) {
+		printf("Unexpected value in flag I, expected %d, was %d", expected, state->flags.i);
+		exit(1);
+	}
+}
+
+void assert_flag_d(State6502* state, byte expected) {
+	if (state->flags.d != expected) {
+		printf("Unexpected value in flag D, expected %d, was %d", expected, state->flags.d);
+		exit(1);
+	}
+}
+
+void assert_flag_v(State6502* state, byte expected) {
+	if (state->flags.v != expected) {
+		printf("Unexpected value in flag D, expected %d, was %d", expected, state->flags.v);
+		exit(1);
+	}
+}
 ////////////////////////////////////////
 
 
@@ -1237,6 +1264,92 @@ void test_DEC_ZP_wraparound() {
 	test_cleanup(&state);
 }
 
+// FLAGS
+
+void test_SEC() {
+	State6502 state = create_blank_state();
+	
+	char program[] = { SEC };
+	memcpy(state.memory, program, sizeof(program));
+	test_step(&state);
+
+	assert_flag_c(&state, 1);
+
+	test_cleanup(&state);
+}
+
+void test_CLC() {
+	State6502 state = create_blank_state();
+	state.flags.c = 1;
+	char program[] = { CLC };
+	memcpy(state.memory, program, sizeof(program));
+	test_step(&state);
+
+	assert_flag_c(&state, 0);
+
+	test_cleanup(&state);
+}
+
+void test_SED() {
+	State6502 state = create_blank_state();
+
+	char program[] = { SED };
+	memcpy(state.memory, program, sizeof(program));
+	test_step(&state);
+
+	assert_flag_d(&state, 1);
+
+	test_cleanup(&state);
+}
+
+void test_CLD() {
+	State6502 state = create_blank_state();
+	state.flags.d = 1;
+	char program[] = { CLD };
+	memcpy(state.memory, program, sizeof(program));
+	test_step(&state);
+
+	assert_flag_d(&state, 0);
+
+	test_cleanup(&state);
+}
+
+void test_SEI() {
+	State6502 state = create_blank_state();
+
+	char program[] = { SEI };
+	memcpy(state.memory, program, sizeof(program));
+	test_step(&state);
+
+	assert_flag_i(&state, 1);
+
+	test_cleanup(&state);
+}
+
+void test_CLI() {
+	State6502 state = create_blank_state();
+	state.flags.i = 1;
+	char program[] = { CLI };
+	memcpy(state.memory, program, sizeof(program));
+	test_step(&state);
+
+	assert_flag_i(&state, 0);
+
+	test_cleanup(&state);
+}
+
+void test_CLV() {
+	State6502 state = create_blank_state();
+	state.flags.v = 1;
+	char program[] = { CLV };
+	memcpy(state.memory, program, sizeof(program));
+	test_step(&state);
+
+	assert_flag_v(&state, 0);
+
+	test_cleanup(&state);
+}
+
 /////////////////////
 
 typedef void fp();
@@ -1250,7 +1363,7 @@ fp* tests_sty[] = { test_STY_ZP, test_STY_ZPX, test_STY_ABS };
 fp* tests_inx_iny_dex_dey[] = { test_DEX, test_DEX_wraparound, test_DEY, test_DEY_wraparound, test_INX, test_INX_wraparound, test_INY, test_INY_wraparound };
 fp* tests_txa_etc[] = { test_TXA, test_TAX, test_TYA, test_TAY };
 fp* tests_inc_dec[] = { test_INC_ZP, test_INC_ZP_wraparound, test_INC_ZPX, test_INC_ABS, test_INC_ABSX, test_DEC_ZP, test_DEC_ZP_wraparound };
-
+fp* tests_flags[] = { test_CLC, test_SEC, test_CLD, test_SED, test_SEI, test_CLI, test_CLV };
 #define RUN(suite) run_suite(suite, sizeof(suite)/sizeof(fp*))
 
 void run_suite(fp * *suite, int size) {
@@ -1270,4 +1383,5 @@ void run_tests() {
 	RUN(tests_inx_iny_dex_dey);
 	RUN(tests_txa_etc);
 	RUN(tests_inc_dec);
+	RUN(tests_flags);
 }
\ No newline at end of file