Coronary collateral circulation usually develops as a consequence of recurrent ischemia associated with severe stenosis. In exceptional cases, it can develop with moderate coronary lesions if there is severe recurrent vasospasm. In this situation, the presenting clinical features of vasospastic angina (i.e., effort angina with ST-segment depression) can be identical to those of a severe permanent lesion. We present a patient who exhibited effort angina and ST-segment depression on treadmill testing. Angiography showed severe right coronary artery stenosis and the development of coronary collateral circulation from the other main artery. After repeated intracoronary bolus injection of nitroglycerin, only a moderate stenosis was still apparent and the collateral circulation had disappeared.