In a randomised controlled evaluation of multifactorial prevention of coronary heart disease (CHD) among 60 881 men employed in 80 factories in Belgium, Italy, Poland, and the UK intervention was associated with reductions of 10.2% in total CHD, 6.9% in fatal CHD, 14.8% in non-fatal myocardial infarction, and 5.3% in total deaths, with a neutral result for non-CHD deaths. Benefit was significantly related to the extent of risk factor change. The observed reduction in total CHD was 62% of that predicted by means of a multiple logistic function summary of risk factor changes. Advice on risk factor reduction in middle-aged men is effective to the extent that it is accepted and it appears to be safe.