BACKGROUND: Recently, according to many studies, variable factors have been known to be associated with physical fitness. The factors such as obesity and inactivity are associated with poor physical fitness, but regular exercise is associated with good physical fitness. In our country, these studies are not yet reported. And so, this study was designed to investigate the factors associat,ed with physical fitness. METHODS: From May 1st, until July 30th 1996, we recruited the 411 subjects who visited the Health Promotion Center at Seoul National University Hospital. Data related to sex, age, exercise, job, cigarette smoking, alcohol consumption were obtained by self-administered Questionnaire. Obesity index was calculated by the percentage of standard body weight. And VO2max were obtained by submaximal bicycle ergometer test. High level exercise group was defined as the persons who had taken exercise more than 3 times a week and 20 minutes per session, and moderate exercise group was defined as the persons who had taken exercise one or two times a week and 20 minutes per session, and sedentary group was defined as the persons who had taken exercise more than 20 minutes less than one time per week. RESULTS: The subjects were 230 males(56%), total numbers were 411. The results were as follows. Compaired to women and nonexercise group, men and exercise group had high VO2max(p<0.005). The relationship between VO2max and age showed negative, and the VO2max of obese group(obesity index>_120) was greater than that of nonobese group. Any significant relationships between VO2max and job, disease were not found. In multiple regression analysis, significant relationships between VO2max and age, sex, exercise type, and obesity index were observed(p<0.01). CONCLUSIONS: We concluded that there were significant relationships between VO2max and obesity index, exercise group.