Context: Recombinant human GH (rhGH) improves growth and body composition in glucocorticoid-treated children. Its effects on muscle strength are poorly evaluated. Objectives: Our objective was to evaluate rhGH effects on muscle strength in children receiving long-term glucocorticoid therapy; effects on height SD score (SDS) and body composition were assessed also. Design and Setting: A randomized, controlled, delayed-start study of rhGH for 12 months was started after randomization (baseline) or 6 months later (M6). Patients: Patients included 30 children with various diagnoses. Intervention: rhGH was administered at 0.065 mg/kg/d for 6 months and then in the dosage maintaining serum IGF-I levels below +2 SDS for chronological age. Main Outcome Measures: The primary criterion was the between-group difference in composite index of muscle strength (CIMS) change at M6. Secondary criteria included between-group differences in CIMS SDSheight, lean mass (LM), thigh muscle area (MA), and height SDS changes at M6; these parameters were also assessed in the overall population after 1 year of rhGH therapy. Results: At M6, rhGH therapy did not significantly affect changes in CIMS or CIMS SDSheight (+17.6% vs +7.5% and +0.14 ± 0.38 vs +0.11 ± 0.62, respectively); the rhGH-treated group had significantly larger changes in height SDS (+0.2 [0.3] vs −0.2 [0.3]; P = 0.003), LM (+7.3% [+3.7%; +21.6%] vs 0% [−4.7%; +3.2%]; P = 0.002), and MA (+8.8% [+5%; +15.6%] vs. −0.6% [−6.3%; +7.7%]; P = 0.01) compared with the untreated group. After 1 year of rhGH, height SDS, LM, and MA increased significantly, CIMS increased by 24.7% (+5.8%; +34.2%), and CIMS SDSheight remained within the normal range. Conclusions: rhGH increased height, LM, and MA. However, muscle strength did not improve significantly.