Maximal oxygen uptake (Vo2max) was estimated in 1,200 sedentary men aged 18 to 50 years and in 400 active athletes aged 18 to 30 years participating in 10 different kinds of sport. The Vo2 in the 18- to 30-year-old sedentary group was 34.3 +/- 9.7 (SD) ml - kg-1 - min-1, and in the 31- to 40- and 41- to 50-year age groups a similar value of 28.1 +/- 9.9 ml - kg-1 - min-1 was recorded. The results in the sedentary group were lower than those recorded in active populations in other countries by 20 to 40%, possibly due to lack of physical activity. The mean Vo2max in 400 active athletes was 54.8 +/- 10.0 ml - kg-1 - min-1, which is very similar to Vo2max values recorded in active populations in other countries. The difference between the mean Vo2max of the 18- to 30-year-old sedentary group and that of the active one was found to be signifcant (P less than 0.005). The highest mean Vo2max values among the athletes were recorded in the group of long-distance runners (60.8 ml - kg-1 - min-1) and cyclists (61.9 ml - min-1), while unexpectedly low mean Vo2max values were recorded in the group of swimmers (50.1 +/- 8.1 ml - kg-1 - min-1) and football players (51.7 +/- 9.1 ml - kg-1 - min-1).