Blood pressure was recorded at rest and during exercise (n = 577) in 810 male sportsmen. Larger subgroups included 125 cyclists, 98 long-distance runners, 90 cross-country skiers, 108 players of various ball games, 25 weight-lifters, and 29 swimmers. At rest, hypertension was observed in 3.8% and borderline hypertension in 7.8% of the sportsmen investigated. When blood pressure responses during exercise were also included, values were increased by 28% to 4.9% (hypertension) and by 26% to 9.8% (borderline hypertension). In the sportsmen investigated, the age range 14-29 years was overrepresented. The age-corrected prevalence was 5.4% (hypertension) and 11.1% (borderline hypertension) at rest. The prevalence of increased blood pressure in sportsmen was about half of the prevalence expected for the total population (p less than 0.05). The low incidence of hypertension in sportsmen may be due to physical training as well as to genetic factors. Increased blood pressure was significantly more frequent in swimmers and weight-lifters than in the other investigated subgroups. In these two sports, unfavorable training-specific factors may compensate for the possible beneficial effects of physical training.