The autors analyzed potential differences in cardiorespiratory endurance, blood lipid levels, and body composition in 17 sedentary women (X̄ V̇O(2max) = 33.9 ml · kg-1 · min-1) ages 18 to 40 years (X̄ = 28), resulting from chronic miniature trampoline (rebounder) exercise. After preliminary evaluation that included repeated symptom-limited treadmill exercise tests (TGXT) and rebounding tests with oxygen consumption, subjects were randomly assigned either to an exercise or to a control group. Exercise sessions were conducted 5 days per week for 11 weeks and consisted of two 15-minute periods with 5 minutes rest between periods. Subjects bounced and/or ran in place on the rebounder at a rate necessary to maintain a prescribed training heart rate (70 to 85% of maximal TGXT heart rate). Posttraining testing revealed a 4.4% improvement in V̇O(2max) for the rebounding group and no significant change for the control group (P<0.05). No significant differences were observed between groups for body weight, percent body fat, and total and HDL cholesterol and triglyceride levels. Thus, 11 weeks of rebounding exercise under the conditions described resulted in only minimal improvement in cardiorespiratory fitness and no significant changes in blood lipid levels or body composition. Limited findings from previous studies of cardiac patients, among others, suggest benefits to these populations from rebounding exercise. Given the convenience of this exercise, as well as the major advantage of its apparent low level of trauma to the musculoskeletal system, further study is essential to ascertain the extent to which rebounding might be beneficial among a variety of populations.