A six-year intervention study of the feasibility and effectiveness of a program aimed at the primary prevention of coronary heart disease (CHD) has been initiated among children in six school districts in Westchester County, New York. Schools randomly were assigned either to the intervention program or to a control group. The intervention program consists of a curriculum focusing on nutrition, physical fitness, and cigarette smoking prevention. The study population at baseline comprised 1,822 fourth-graders. This paper presents the findings at baseline and at one-year follow-up for the following target risk factors: systolic and diastolic blood pressure, plasma total and high-density lipoprotein (HDL) cholesterol, serum thiocyanate, ponderosity index, triceps skinfold thickness, and postexercise pulse recovery rate. After one year of intervention, the program was found to be acceptable to school administrators, teachers, parents, and children. Small net changes in the favorable direction were observed for diastolic blood pressure and thiocyanate. Intervention programs in schools may, after sufficient duration, prove to be effective in lowering CHD risk.