AIM: To assess trends in neuro-muscular and cardio-respiratory fitness and morphological fitness in Swedish adolescents between 1987 and 2001. METHODS: Comparison of data from two samples, one from 1987 (n = 479) and one from 2001 (n = 1470). Subjects underwent functional tests of muscular strength in the lower limbs, trunk and upper body, sub-maximal ergometrics, and measurement of body mass and height. RESULTS: Cardio-respiratory fitness showed only small changes between 1987 and 2001 among boys, with no changes in girls. Neuro-muscular fitness, as measured by three functional tests, was lower in 2001 compared to 1987. The most pronounced changes in these functional tests were found in the arm-hang test, while changes in lower body and trunk strength tests were less. Our results indicate that the difference in the prevalence of overweight in adolescents between 1987 and 2001 is mainly due to a large change in the most unfit group. The fittest group showed only marginal changes. CONCLUSION: We suggest that the differences in neuro-muscular fitness are at least partly due to differences in the amount and nature of physical activity, and that this might lead to consequences for health later in life.