The purpose of this study was to investigate the effect of 1-year diet intervention, exercise intervention and both combined on blood pressure (BP) in normotensives and mild hypertensives. Two hundred and nineteen sedentary middle aged men and women with slightly deranged coronary heart disease (CHD) risk factors were randomised to a control, a diet, an exercise and a diet + exercise group. Based on baseline diastolic BP, participants were divided into tertiles, giving baseline average BP of 141.4/96.7 in tertile 1, 130.7/87.6 in tertile 2 and 121.9/79.0 in tertile 3. The 1-year net-difference in BP between the intervention groups and the control group decreased across the tertiles; in tertile 1 being -11.2/-6.7 (p < 0.05), -11.3/-6.7 (p < 0.05 for systolic BP only) and -7.0/-5.1 (NS) in the combined, diet and exercise group respectively. Triglycerides, HDL cholesterol, and insulin variables were significantly and favourably changed, the changes being most marked in the combined group. The results show that diet and diet + exercise are about equally effective in reducing BP, and the effects may be dependent on the baseline level. Within the upper tertile of baseline BP, the decline in BP in the combined intervention and the diet group are almost comparable to those obtained with drug treatment. In addition, other important CHD risk factors were all changed in a beneficial direction.