W.H.O. European Collaborative Group (Chariman: Rose, G., Epidemiology Dept., St. Mary's Hospital Medical School, London, W.2, England). An international controlled trial in the multifactorial prevention of coronary heart disease. Int. J. Epid. 1974, 3: 219–224. Centres in Belgium, Italy, Poland and the United Kingdom are collaborating under World Health Organization auspices in a randomized controlled trial, set up in order to estimate (1) the extent to which the main risk factors for coronary heart disease (CHD) can be modified in workers in industry, using primarily a health education approach and with a realistic level of resources; (2) the effect of such changes on CHD incidence and mortality; (3) the consistency of results between different countries. The allocation units are factories or other large occupational units, which permit a community as well as individual approach. The subjects are men in all grades of employment, aged 40–59 years at entry. The intervention measures are (1) cholesterol-lowering diet, (2) cessation of cigarette smoking, (3) physical exercise, (4) control of overweight, and (5) drug treatment of hypertension.