Relationships between adolescent physical fitness and adult health-related fitness were investigated. Forty-five subjects (20 males, 25 females) participated in physical fitness tests in 1976 and again in 2001. The adolescent physical fitness tests were distance running (2,000 m for boys or 1,500 m for girls), 50 m run, pull-ups (boys) or flexed arm hangs (girls), shuttle run, a 30-sec sit-up test, standing broad jump, hand grip-test, and sit-and-reach test. The adult health-related physical fitness index (APFI), stratified by sex, was formed by summing the z-scores of a bicycle ergometer test, sit-up test, hand-grip test, and sit-and-reach test. Height- and weight-adjusted correlations between adolescence and adulthood for exactly similar tests for men and women were, respectively, 0.74 (95% CI, 0.44-0.89) and 0.53 (95% CI, 0.17-0.76) in sit-and-reach tests, 0.41 (95% CI, -0.04 to 0.72) and 0.55 (95% CI, 0.20-0.78) in sit-up tests, and 0.53 (95% CI, 0.11-0.44) and 0.44 (95% CI, 0.05-0.71) in hand-grip tests. When all adolescent tests were put in regression analysis together with BMI in 2001, the significant explanatory factors for APFI were distance running ability and the sit-and-reach test for men and sit-up test, flexed arm hang, and BMI in 2001 for women.