On screening 192 men and women aged 35-64 were identified as having two or more of the following risk factors: blood pressure greater than or equal to 140/90 mm Hg, plasma cholesterol concentration greater than or equal to 6.3 mmol/l (243.6 mg/100 ml), and current smoking habit greater than or equal to 10 cigarettes a day. They were randomly allocated to a group for modification of behaviour or to serve as controls. Both groups were given health education leaflets containing advice to stop smoking, to reduce animal fats in the diet, and on the importance of reducing blood pressure. In addition, the treatment group had group sessions of one hour a week for eight weeks in which they were taught breathing exercises, relaxation, and meditation and about managing stress. It had previously been found that after eight weeks and eight months there was a significantly greater reduction in both systolic and diastolic blood pressures in the group taught to relax compared with the control group. After four years of follow up these differences in blood pressure were maintained. Plasma cholesterol concentration and the number of cigarettes smoked were lower in the treatment group at eight weeks and eight months but not at the four year follow up. At four years more subjects in the control group reported having had angina and treatment for hypertension and its complications. Incidence of ischaemic heart disease, fatal myocardial infarction, or electrocardiographic evidence of ischaemia was significantly greater in the control group. If the results of this study could be obtained in a larger study the financial and health care implications would be enormous.