The left IMA graft to the LAD showed a string sign with no antegrade flow in an asymptomatic 67-year-old man 3 years after the operation. The LAD lesion had regressed from 95% stenosis to less than 50% during this period. Exercise electrocardiographic and thallium 201 myocardial scintigraphic examinations revealed no ischemia in the LAD region. When the LAD was temporarily occluded by a PICA balloon, the anterograde flow from the IMA to the LAD could be demonstrated by angiography. The IMA graft in no flow situation has maintained anatomical patency for 3 years after the operation.