The aim of this study was primarily to investigate differences in onset and progression of puberty, body composition, and growth between groups of young female gymnasts, schoolgirls and girl swimmers, and secondly to determine the relations between the pubertal events and body composition, especially the amount of body fat, or training activities. In 1980, 1981, and 1982, 668 female gymnasts, 298 schoolgirls and 98 girl swimmers were examined. The gymnasts were subdivided into three different groups, namely, the talented, the nontalented, and the selection group. The onset of puberty and menarche was delayed in the gymnastic groups by about 1 or 2 years compared to the schoolgirls and girl swimmers. The gymnasts were on average smaller than the schoolgirls and girl swimmers. These differences became even more pronounced after the age of 10 years. This may be caused by a delayed growth spurt within the gymnastic groups in combination with self-selection. Furthermore, the gymnasts were leaner than the other two groups: the girl swimmers had a greater fat mass and a greater lean body weight, while the schoolgirls had more fat mass. Relations were found between the parameters of pubertal development and calculated fat mass and also between breast development, pubic hair growth and age, body height, body weight, and calculated lean body weight. Only in the swimming group were training hours per week related to body height, body weight, lean body weight, and pubic hair growth.