A five-year intervention study of the effectiveness of the "Know Your Body" program in reducing coronary heart disease risk factors among black students in the District of Columbia, who were in grades 4-6 at baseline, was begun in 1983. Nine schools were stratified on socioeconomic status and randomly assigned to control and intervention groups. The "Know Your Body" curriculum focuses on nutrition, fitness, and the prevention of cigarette smoking. At baseline, 1,234 students were eligible for the screening in which the following target risk factors were measured: systolic and diastolic blood pressures, ponderosity index, triceps skinfold thickness, postexercise pulse recovery rate, serum total and high density lipoprotein (HDL) cholesterol, and serum thiocyanate. After two years of intervention, results indicated that the program may have had a favorable impact on the following risk factors: systolic and diastolic pressures, HDL cholesterol, ratio of total to HDL cholesterol, fitness (postexercise pulse recovery rate), and smoking. Significant net changes in the favorable direction also were found for health knowledge and attitude toward smoking. Blood pressure reduction was associated with decreased ponderosity and improved fitness, and increased HDL cholesterol was associated with decreased ponderosity. These results are consistent with other evaluations of the "Know Your Body" program, suggesting that the program may be effective in reducing chronic disease risk in diverse school populations.