A single blind, placebo controlled, dose-ranging 3 month study of the effects of enalapril on cardiovascular parameters, clinical status and self-paced exercise capacity was undertaken in 12 Nigerians with chronic heart failure. Enalapril exerted only a modest reduction in blood pressure and heart rate but significantly improved functional capacity (P less than 0.01), and prolonged self-paced exercise time (P less than 0.05) compared to the placebo baseline. The pressure rate product and the double product corrected for exercise time, an index of myocardial oxygen demand, exhibited a significant and sustained reduction on enalapril treatment (P less than 0.01). Concentration of sodium in the serum was significantly increased (P less than 0.05) but concentrations of potassium and creatinine were unaltered. These results demonstrate the sustained efficacy of enalapril in black Africans with heart failure and indicate no important racial difference in the response to inhibition of angiotensin converting enzyme in congestive heart failure.