The purpose of this study was to determine the effects of a 15-week aerobic activity program on the total cholesterol (TC) and high-density lipoprotein cholesterol (HDL-C) levels of 25 high school students, ages 14–17 years (experimental group = 14, control group = 11). Participants in the activity program exercised 4 days per week in a specially designed physical education class, while the control group participated in the regular physical education program. Results of the analysis of covariance found significant reductions in TC in the training group (control group Adj M = 190.2 mg/dl, experimental group Adj M = 173.1 mg/dl, p >. 05), but no significant changes in HDL-C (control group Adj M = 49.8 mg/dl, experimental group Adj M = 50 mg/dl). While the exercise program appeared to have a beneficial effect on TC in 12 of 14 participants (86%), HDL-C also dropped in 12 of 14 participants (86%). © 1997 by the American Alliance for Health, Physical Education, Recreation and Dance.