The purpose of this study was to determine the effects of recombinant human GH (rhGH; 0.025 mg/kg.day) and one of two doses of recombinant human insulin-like growth factor-I (rhIGF-I; 0.015 and 0.060 mg/kg, twice daily) on body composition in elderly women. Sixteen healthy elderly women (mean age +/- SEM, 71.9 +/- 1.3 yr) were randomly assigned to receive either rhGH (GH; n = 5), low dose rhIGF-I (n = 6), or high dose rhIGF-I (n = 5). A 2-week predrug baseline period was followed by 4 weeks of hormone treatment, with a standardized diet fed throughout. All groups experienced a significant increase in serum IGF-I and IGFBP-3 levels over the treatment period, accompanied by significant decreases in IGF-II (P < 0.05). Fat mass decreased in all groups, with significant increases in lean body mass and nitrogen retention occurring in the high dose IGF and GH groups. Total body water did not change, whereas increases observed in intracellular fluid approached significance (P = 0.06). These anabolic changes were accompanied by numerous negative side-effects in the GH and high dose IGF groups, including headaches, lethargy, joint swelling/pain, and bloatedness. The low IGF dose was well tolerated. These results demonstrate that the administration of rhGH and rhIGF-I for 4 weeks results in anabolic changes in body composition in elderly women.