Prior studies of premature coronary artery disease (CAD) in young adults did not address the association of race/ethnicity and risk factors. Therefore, the authors conducted a study of 400 patients 40 years and older undergoing coronary angiography at a large, urban public hospital that serves predominately minority, uninsured populations. The prevalence of risk factors and their association with premature CAD varied markedly by ethnic group. Among blacks, dyslipidemia, diabetes, and smoking were independently associated with premature CAD. Among Hispanics, dyslipidemia, male sex, and family history of CAD were independently associated with premature CAD. Smoking was the only risk factor in whites, and no independent risk factor was identified in Asian Indians. Whites and Asian Indians had a higher prevalence of disease than blacks or Hispanics - before and after adjusting for risk factor imbalances across ethnic groups. In this ethnically diverse population, the authors' findings underscore the importance of identifying distinctive risk factors in various ethnic groups.