A case of coronary artery bypass grafting (CABG) for single coronary artery (SCA) complicated by effort angina pectoris was reported. A 52-year-old man was admitted complaining of effort angina. Coronary arteriography demonstrated a single coronary artery originated in left coronary sinus bifurcated to the left anterior descending artery (LAD) and the circumflex artery (CX) which extended around the atrio-ventricular fold to send a branch down the posterior small branches extend to posterior surface of the right ventricle. This type single coronary artery was classified to Smith's type I. Other findings included 75% stenosis in LAD #6 and #7, 90% stenosis in CX #11. CABG was carried out using left internal thoracic artery graft and saphenous vein graft. His postoperative course was uneventful. Anginal discomfort disappeared, and favorable results was obtained. SCA might be vulnerable to ischemic insult, so that coronary revascularization should be recommended in selected cases before the onset of serious complications.