This study was conducted to examine the relationship between physical fitness and all-cause mortality in Japanese men. We evaluated the physical fitness and risk for all-cause mortality of 9,986 Japanese men who were given a submaximal exercise test and a medical examination between 1982 and 1984. Physical fitness was measured using a bicycle ergometer test, and maximal oxygen uptake was estimated. The average follow-up time was 14 years, for total of 139,836 person-years of observation. There were 247 deaths during the observation period. The relative risk and 95% confidence intervals (95% CI) for all-cause mortality were obtained using the Cox proportional hazards model. Following age adjustment, and using the lowest physical fitness (quintile I) group as a reference, the hazard ratios for quintiles II through V were, 0.54 (0.39-0.77), 0.66 (0.47-0.94), 0.58 (0.39-0.86), and 0.46 (0.27-0.78), respectively. After being adjusted for age, body mass index, hypertension, and urinary protein, the hazard ratios were, 0.52 (0.37-0.73), 0.60 (0.42-0.87), 0.50 (0.33-0.75), and 0.39 (0.22-0.67), respectively. The results presented here support the hypothesis that a low level of physical fitness in an important risk factor for all-cause mortality in Japanese men.