We examined the distribution of physical activity among different occupations in Japan. A questionnaire was sent to full-time employees at nine companies in Japan between 1996 and 1998, with an average response rate of 85.2%. Data from 20,654 respondents (17,637 male and 3017 female) were analyzed. We classified the occupations into eight groups according to the International Standard Classification of Occupations (1988). Daily energy expenditure, weekly physical activity, and monthly leisure-time physical activity (LTPA) were measured using a physical activity questionnaire and some additional questions. In males, LTPA was significantly different among occupations, with clerks having greater physical activity than managers and blue-collar workers (P<0.001). The pattern was similar even after adjusting for education, age, and working hours. In females, the difference among occupations was not clear. The distribution of LTPA among occupations exhibits a "barrel-shape" in Japan. It was higher for intermediate class occupations such as clerks, which was in agreement with a lower coronary heart disease mortality observed in intermediate class occupations among Japanese male employees.