We conducted an epidemiologic study to examine the extent to which differences in purported risk factors account for black-white differences in risk of idiopathic dilated cardiomyopathy. We examined associations with race and other factors by comparing newly diagnosed cases (N = 122), ascertained from five Washington DC area hospitals, with neighborhood controls (N = 234) identified using a random digit dialing technique. We matched the cases and controls on sex and 5-year age intervals and analyzed the data using conditional logistic regression methods. We found that blacks were at increased risk for idiopathic dilated cardiomyopathy (relative odds = 2.6, 95% confidence interval = 1.6-4.3). The increased risk for blacks could not be explained by income, educational attainment, alcohol consumption, cigarette smoking, or history of hypertension, obesity, diabetes, or asthma. We also observed a possible interactive effect between black race and hypertension.