Of the 12,866 males aged 35 to 57 years who were randomly assigned to the special intervention (SI) and usual care (UC) groups of the Multiple Risk Factor Intervention Trial (MRFIT), 931 (7.2%) were black. With use of a multivariate score from the Framingham study, all were assessed to be in the upper 10% to 15% of coronary risk because of their diastolic blood pressure, serum cholesterol level, and/or cigarette use. Blacks in the MRFIT were of lower educational and income levels and were less often employed in professional-technical-managerial or other white-collar jobs than whites. At baseline, blacks had higher mean blood pressures and a higher prevalence of hypertension than whites, were more often smokers but smoked fewer cigarettes per day, and had a higher prevalence of ECG abnormalities. Dietary lipid composition was similar for black and white males; so also were weight and body mass index, plasma total cholesterol levels, and low-density lipoprotein (LDL) cholesterol levels. High-density lipoprotein cholesterol levels were higher and triglyceride levels lower for blacks than whites. Attendance rates over the years of the trial were similarly high for blacks and whites. Among males in the SI group, smoking cessation rates, changes in dietary lipid composition and in plasma total and LDL cholesterol, and achievement of normotensive diastolic pressure with antihypertensive stepped-care treatment were comparable for black and white males. This MRFIT experience indicates ability to induce extensive changes in life-styles (eating and smoking habits) of both black and white American males of varying educational and socloeconomic backgrounds and also to achieve long-term effective adherence to programs for the treatment and control of hypertension.