Objective To examine whether restriction of caloric intake and exercise of vigorous intensity can independently and additively influence clinic and ambulatory blood pressures in sedentary overweight men.Design Sixty subjects aged 20-50 years were randomly allocated either to continue their normal caloric intake or to restrict it by 4186-6279 kJ/day, with 15% provided by protein, 30% by fat and 55% by carbohydrate, for 16 weeks, Within each of these groups subjects randomly allocated either to a control programme of exercise or to a vigorous intensity programme of exercise for 30 min three times a week The light exercise group performed stationary cycling against no resistance, flexibility exercises and slow walking, The vigorous intensity group cycled on an ergometer at 60-70% of maximum their workload.Results Fifty-one subjects completed the study. Their maximal oxygen uptake was increased by approximately 24%, with vigorous exercise but did not change with light exercise. Caloric intake restriction led to a significant loss of body mass of 9.5 kg (95% confidence interval 7.6-11.3), whereas vigorous exercise had no effect Restriction of caloric intake reduced supine clinic systolic and diastolic blood pressures significantly by 5.6 (2.3-8.9) and 2.4 mmHg (0.4-4.2), respectively. Relative to the control light exercise group, exercise of vigorous intensity exercise had no significant effect on clinic blood pressure, In contrast, time series analysis revealed that both caloric intake restriction and vigorous exercise were associated with lower daytime ambulatory systolic blood pressure, the reduction in systolic blood pressure being sustained throughout the 24h period when vigorous exercise and caloric intake restriction were combined.Conclusion Compared with the effects of caloric intake restriction, the effects of a vigorous exercise programme on blood pressure are inconsistent, there being no influence on clinic blood pressure but a reduction in daytime ambulatory blood pressure. However, when combined with caloric intake restriction, regular vigorous exercise exhibits a synergistic effect in reducing ambulatory blood pressure throughout a 24h period.