. We studied 4316 men aged 45-69 years (who had not suffered a previous myocardial infarction or stroke) identified at screening in 81 general practices in the UK as being at high risk of coronary heart disease. The changes in the prevalence of smoking and in blood pressure, serum cholesterol level, body mass index and plasma fibrinogen level were recorded for a period of up to 2 years after entry into the trial