We reviewed the ambulatory medical record to determine eligibility and to collect information on key covariates for the period before the index date. We collected information on medical history, including angina, hypertension, diabetes, congestive heart failure, myocardial infarction, transient ischemic attack, and peripheral vascular disease, and information on traditional risks factors such as blood pressure and smoking status. Angina was defined as probable or definite based on the notes of the primary care physician and consultants and the results of diagnostic tests. Diabetes mellitus was defined as treatment with oral hypoglycemic medication and/or insulin or a history of diabetes. Hypertension was defined as treatment with antihypertensive medications. Blood pressure was the blood pressure measured during the most recent visit before the index date. Cardiovascular disease was defined as any of following conditions: prior myocardial infarction, angina, angioplasty, coronary artery bypass, carotid endarterectomy, peripheral vascular disease procedure, transient ischemic attack, claudication, congestive heart failure, or atrial fibrillation. We also performed a telephone interview of consenting survivors to assess risk factors such as smoking status, education, and race.