BACKGROUND: Risk factors for coronary heart disease events have most commonly been evaluated in healthy men. OBJECTIVE: To assess risk factors, event rates, and use of secondary prevention treatments in women with preexisting coronary disease. DESIGN: A prospective cohort of clinical trial participants. SETTING: 20 U.S. clinical centers. PARTICIPANTS: 2763 postmenopausal women with known coronary disease in the Heart and Estrogen/progestin Replacement Study (HERS). MEASUREMENTS: Myocardial infarction or death from coronary heart disease. RESULTS: On multivariable analysis, the researchers found 11 risk factors: 6 noted by history (nonwhite ethnicity, lack of exercise, treated diabetes, angina, congestive heart failure, and more than one previous myocardial infarction) and 5 that were measured (blood pressure, low-density lipoprotein cholesterol level, high-density lipoprotein cholesterol level, lipoprotein(a) level, and creatinine clearance). The annual rate of coronary events was 1.3% (95% CI, 0.7% to 2.5%) in women with no risk factors and 8.7% (CI, 7.1% to 10.8%) in women with five or more risk factors (a sixfold increase). At entry into HERS, 83% of participants were receiving aspirin or other antiplatelet agents, 33% were receiving beta-blockers, 18% were receiving angiotensin-converting enzyme inhibitors, and 53% were receiving lipid-lowering drugs. Women with more risk factors were less likely to be taking aspirin (P < 0.001) and lipid-lowering drugs (P = 0.006). CONCLUSIONS: Women with coronary disease are at high risk for myocardial infarction or death from coronary heart disease even in the absence of other risk factors, and their risk increases up to sixfold when many risk factors are present. Established drugs for secondary prevention, including aspirin, beta-blockers, and lipid-lowering agents, are underused in these women, especially those at highest risk.