The Belgian Heart Disease Prevention Project was a controlled, randomized multifactorial intervention trial in middle-aged men which lasted 6 years. Significant net differences between intervention and control groups were observed in change in risk profile, in total mortality and in CHD incidence. The net difference in risk profile change was greatest at two years, intermediate at four years and minimal at six years. Total and cause-specific mortality rates were systematically followed from the 6th to the 10th year. Follow-up at 10 years was 99.3% complete. The differences between intervention and control groups in total, coronary and cardiovascular mortality reduced from the 6th to the 10th year. The results suggest that changes in risk profile are rapidly followed by changes in cardiovascular mortality, but this applies in both directions. Thus risk reduction should be maintained in order to achieve a long-lasting preventive effect.