The Puerto Rico Heart Health Program is an observational epidemiological study of coronary heart disease (CHD) among 9824 Puerto Rican men conducted from 1965 to 1980. Increased level of education was associated with decreased total mortality and increased CHD incidence among the urban participants. Urban men with more education, age 45-64, also showed higher levels of blood pressure and serum cholesterol, more obesity, less physical activity and more atherogenic diets. The increased level of risk factors among those with high education could statistically account for the elevations in CHD incidence. Among rural participants there was an increase in total mortality among those at the highest and lowest levels of education.