The feasibility and effectiveness of a hospital-based exercise-training program followed by a home-based program for improving fitness, strength, and changes in body composition in children and adolescents with HIV were evaluated. Subjects participated in nonrandomized 24-session, hospital supervised exercise training program followed by an 314 unsupervised home-based maintenance program. Outcome measurements included muscular strength/endurance, flexibility, relative peak VO(2), body composition, and lipids. Seventeen subjects (eight females) with a median age of 15.0 years (range: 6.0-22.6) and BMI z-score of 0.61 (range: -1.70-2.57) at entry completed the intervention. After 24 training sessions, the median increases in muscular strength were between 8% and 50%, depending on muscle group. The median increases in muscle endurance, relative peak VO(2), and lean body mass were 38.7% (95% CI: 12.5-94.7; p = 0.006), 3.0 ml/kg/min (95% CI: 1.5-6.0; p < 0.001), and 4.5% (95% CI: 2.4-6.6; p < 0.001), respectively. Twelve children completed the home-based maintenance program. Median changes in these outcomes between completion of the hospital-based intervention and a follow-up after completion of the home-based program were near zero. No adverse events occurred during the intervention. A supervised hospital-based fitness program is feasible, safe, and effective for improving general fitness and strength as well as lean body mass in children with HIV.