1. Although several epidemiological studies have not observed significant independent relationships between physical activity or fitness and blood pressure, others have concluded that blood pressure is lower in individuals who are more fit or active. However, longitudinal intervention studies are more appropriate for assessing the effects of physical activity on blood pressure. 2. Previously, we have performed meta-analyses of randomized controlled trials involving dynamic aerobic endurance training or resistance training. Inclusion criteria were: random allocation to intervention and control; physical training as the sole intervention; inclusion of healthy sedentary normotensive and/or hypertensive adults; intervention duration of at least 4 weeks; availability of systolic and/or diastolic blood pressure; and publication in a peer-reviewed journal up to December 2003. 3. The meta-analysis on endurance training involved 72 trials and 105 study groups. After weighting for the number of trained participants, training induced significant net reductions of resting and day time ambulatory blood pressure of 3.0/2.4 mmHg (P < 0.001) and 3.3/3.5 mmHg (P < 0.01), respectively. The reduction of resting blood pressure was more pronounced in the 30 hypertensive study groups (-6.9/-4.9) than in the others (-1.9/-1.6; P < 0.001 for all). Systemic vascular resistance decreased by 7.1% (P < 0.05), plasma noradrenaline by 29% (P < 0.001) and plasma renin activity by 20% (P < 0.05). Bodyweight decreased by 1.2 kg (P < 0.001), waist circumference by 2.8 cm (P < 0.001), percentage body fat by 1.4% (P < 0.001) and the Homeostatic Model Assessment (HOMA) index of insulin resistance by 0.31 units (P < 0.01). High-density lipoprotein-cholesterol increased by 0.032 mmol/L (P < 0.05). 4. Resistance training has been less well studied. A meta-analysis of nine randomized controlled trials (12 study groups) on mostly dynamic resistance training revealed a weighted net reduction of diastolic blood pressure of 3.5 mmHg (P < 0.01) associated with exercise and a non-significant reduction of systolic blood pressure of 3.2 mmHg (P = 0.10). 5. In conclusion, dynamic aerobic endurance training decreases blood pressure through a reduction of systemic vascular resistance, in which the sympathetic nervous system and the renin-angiotensin system appear to be involved, and favourably affects concomitant cardiovascular risk factors. In addition, the few available data suggest that resistance training is able to reduce blood pressure.