Physical activity of an endurance nature is supposed to affect the lipoprotein profile in adults as well as in children. When examining this profile in premenarcheal athletes, regard has to be paid to an interfering effect of the rising sex hormone levels due to puberty. Therefore, the purpose of this study was to investigate the plasma lipoprotein levels of premenarcheal athletes in relation to their sex hormone profile. Thirty-six elite gymnasts, 21 recreational gymnasts, 27 girl swimmers, and 25 very little active control girls participated. Their age was about 12 years. The sex hormone profiles of all groups were similar. The swimmers had the lowest level of TC, LDL-C, and TG (P less than or equal to 0.05), and apo A-I was elevated in this group as compared with the others (P less than or equal to 0.05). HDL-C was highest in the recreational gymnasts (P less than or equal to 0.05). The elite group and the control group had similar lipoprotein profiles. After adjustment for T and E-2, no change in variance of the lipoproteins was found. A low correlation existed between apo A-I, E-2, and T (P less than or equal to 0.05). Thus, in this pediatric population, the sex hormones did not play a significant role relative to the levels of plasma lipids or apo A-I. As the body composition correlated very weakly with TG, it is tentative to conclude that the variance found in the lipoprotein profile might be due to differences in physical activity. Moreover, genetic factors may have contributed to the variance.