Diabetes is associated with a two- to fourfold increase in cardiovascular morbidity and mortality, and clinical manifestations of atherosclerosis are the leading causes of death in diabetic populations. Because there are reports of benefits associated with active treatment of ischemia, including revascularization, findings from pathological and angiographic studies confirming more diffuse and distal atherosclerosis in diabetic patients highlight the value of angiography to define the optimal therapeutic strategy in these patients. While coronary angiography cannot be recommended as a screening test for asymptomatic or mildly symptomatic patients with diabetes, it should be emphasized that it is necessary to determine the severity of the underlying atherosclerotic disease, especially the presence of left main, three-vessel or proximal left anterior descending artery disease in patients deemed to be at moderate or high risk on the basis of the clinical evaluation and noninvasive testing. Angiography remains the only helpful modality in determining the suitability of the coronary vessels for either percutaneous interventions or surgical bypass when indicated.