BACKGROUND--Thirty-five percent of type I-diabetic patients are dead of coronary artery disease by age 55 years, and the risk of death is increased eightfold to 15-fold in patients with nephropathy. However, the prevalence of coronary artery disease with respect to age is unknown and few risk factors have been identified. METHODS--One hundred ten insulin-dependent diabetic patients underwent routine pretransplant coronary angiography and cardiac risk factor assessment. Angiograms were evaluated by two angiographers for presence or absence of coronary artery disease (CAD, defined as one or more coronary artery stenoses of 50% or greater in diameter, and no CAD, defined as no stenosis of 25% or greater in diameter, respectively). Prevalence of CAD by age was determined, and associated risk factors were defined. RESULTS--Fifty-two of 110 patients had CAD. Coronary artery disease prevalence increased significantly with age; 13 of 16 patients older than 45 years of age had CAD. For patients 35 years of age or younger, associated risk factors included a family history of premature myocardial infarction, higher hemoglobin A1c level, hypertension for more than 5 years, lower high-density lipoprotein level, and smoking for more than 5 pack-years. For patients between 35 and 45 years of age, associated risk factors included number of years of diabetes, higher hemoglobin A1c levels, and smoking more than 5 pack-years. CONCLUSIONS--In type I-diabetic patients with nephropathy, CAD prevalence increased significantly with age and was found in the majority of patients older than 45 years of age. Coronary artery disease risk factors operative in the general population were significantly associated with CAD in this high-risk group. In addition, a role for hyperglycemia in accelerated atherogenesis was supported by the association of both higher hemoglobin A1c levels and number of years of diabetes with CAD.