We tested the hypothesis that the administration of recombinant human growth hormone (rHGH) and exercise would increase lean body mass (LBM) and muscle strength in burned children to a greater extent than rHGH or exercise separately. Children, ages 7-17 yr, with >40% body surface area burned, were randomized into groups. One group (GHEX, n = 10) participated in a 12-wk in-hospital physical rehabilitation program supplemented with an exercise program and received 0.05 mg. kg(-1). day(-1) of rHGH. A second exercising group (SALEX, n = 13) received saline. A third group (GH, n = 10) received a similar dose of rHGH as GHEX and participated in a 12-wk, home-based physical rehabilitation program without exercise. The fourth group (Saline, n = 11) received saline and participated in a 12-wk, home-based physical rehabilitation program without exercise. The mean (+/-SE) percent change in lean body mass after 12 wk was not significantly different between GHEX (9.0 +/- 2.1%), SALEX (5.4 +/- 1.6%), and GH (5.8 +/- 1.8%) groups (P = 0.33). However, the mean percent change in muscle strength was significantly greater in the GHEX (36.2 +/- 5.4%) and SALEX (42.6 +/- 10.0%) groups than in the GH (-7.4 +/- 4.7%) or Saline (6.7 +/- 4.4%) groups (P = 0.008). In summary, rHGH GHEX, SALEX, and GH alone produced similar improvements in LBM. However, muscle strength was only increased via exercise.