Thirty patients with recurrent symptoms after aortocoronary bypass graft surgery underwent angiography as well as exercise thallium 201 imaging. Exercise imaging has been shown to be highly specific (100 percent in the authors' study) in evaluating paients after bypass surgery. Patients with complete revascularization have normal thallium 201 images. Similarly, exercise-induced defects are seen omly in the presence of incomplete revascularization. There are patients, however, with imcomplete revascularization with normal exercise images, but these patients have at least one patent graft and disease is generally limited to the right coronary artery or the diagonal vessels or their grafts.