This study investigated the development of muscular endurance and strength from the age of 16 to the age of 34 and the fitness components at the age of 34 in men and women. A randomly selected group consisting of 220 boys and 205 girls was tested in 1974 and reinvestigated 18 years later. Muscular endurance and strength increased significantly in 4 of the 5 remeasured tests for the men; bench press increased by 58%, two-hand lift by 20%, hand grip by 16% and Sargent jump by 8%. For the women there was a significant increase in bench press and two-hand lift by 25% and 7% respectively, but hand grip and Sargent jump decreased with a few per cent. The hip and trunk flexion test, sit-up, decreased remarkably in both men (58%) and women (78%). At the age of 16 physical capacity was significantly higher in all tests in the men. This was also the situation at the age of 34 except for VO2 max in ml.kg-1.min-1 and muscular endurance in the back muscles. There were no differences in flexibility between men and women except for less flexibility in the hamstring muscles in the men. The result of the balance test was significantly better in the men.