Background Previous studies have documented sex and racial/ethnic disparities in outcomes after acute myocardial infarction (AMI), but the explanation of these disparities remains limited. In a setting that controls for access to medical care, we evaluated whether sex and racial/ethnic disparities in prognosis after AMI persist after consideration of socioeconomic background, personal medical history, and medical management. Methods We conducted a prospective cohort study of the members (20 263 men and 10 061 women) of an integrated health care delivery system in northern California who had experienced an AMI between January 1, 1995, and December 31, 2002, and were followed up for a median of 3.5 years (maximum, 8 years). Main outcome measures included AMI recurrence and all-cause mortality. Results In age-adjusted analyses relative to white men, black men (hazard ratio [HR], 1.44; 95% confidence interval [CI], 1.26-1.65), black women (HR, 1.47; 95% CI, 1.26-1.72), and Asian women (HR, 1.37; 95% CI, 1.13-1.65) were at increased risk of AMI recurrence. However, multivariate adjustment for sociodemographic background, comorbidities, medication use, angiography, and revascularization procedures effectively removed the excess risk of AMI recurrence in these 3 groups. Similarly, the increased age-adjusted risk of all-cause mortality seen in black men (HR, 1.55; 95% CI, 1.37-1.75) and black women (HR, 1.45; 95% CI, 1.27-1.66) was greatly attenuated in black men and reversed in black women after full multivariate adjustment. Conclusion In a population with equal access to medical care, comprehensive consideration of social, personal, and medical factors could explain sex and racial/ethnic disparities in prognosis after AMI.