The Rome Project of Coronary Heart Disease Prevention is a primary preventive trial carried out among 6,027 working men ages 40-59; 3,131 constituted the treatment group and the remaining 2,896 the control group. The preventive action aimed at reducing mean levels of serum cholesterol (generally through dietary prescription and, in a small number of subjects, by drug treatment), high blood pressure (by drugs), smoking habits (by advice to reduce or stop smoking), overweight (by means of diet), and sedentary lifestyle by increased physical activity). The treatment was carried out during a 6-year period and consisted of individual sessions administered to about one-third of higher-risk subjects, while mass education was administered to all men allocated to treatment. No intervention was offered to the control group. The mean changes in levels of the main coronary risk factors in the treatment vs the control group were computed in different ways. Net changes in the treatment group after 6 years, after adjustment for several confounding variables, were -0.71% for body weight, +0.77% for the cigarette consumption, -3.00% for systolic blood pressure, -5.39% for serum cholesterol, and -18% for the estimated multivariate coronary risk. After 8 years of observation, mortality from all causes was lower by 9.8% (one-tailed P = 0.140) in the treatment than in the control group, whereas mortality from coronary heart disease was lower by 23.7% (one-tailed P = 0.059). The incidence of fatal plus nonfatal coronary heart disease events (hard criteria), which could be measured only for the first 6 years, was reduced by 30.9% (one-tailed P = 0.005) in the treatment as compared with the control group.