Thirty to 60 percent of patients with chronic obstructive pulmonary disease (COPD) are malnourished, and this affects ventilatory muscle function and prognosis for survival adversely. We studied the effect of growth hormone (GH) in malnourished patients with COPD (n = 7, mean FEV1 of 1.1 +/- 0.2 L, 45 +/- 7 percent of predicted values; less than 90 percent of ideal body weight). The subjects received a balanced diet of 35 kcal/kg with 1 g of protein/kg for 1 week (pre-GH). During the following three weeks, they received the same diet plus subcutaneous injections of recombinant methionyl human GH (0.05 mg/kg daily). The subjects had no significant weight gain during the week of diet alone (0.07 +/- 0.11 kg, p = NS) but they had substantial weight gain during the first week of GH treatment (1.37 +/- 0.23 kg, p less than 0.01). Nitrogen balance also improved during GH treatment (+1.6 +/- 0.7 g/day on diet alone vs +3.8 +/- 0.5 g/day on diet plus GH, p less than 0.02). Maximal inspiratory pressure improved by 27 +/- 8 percent after GH treatment (p less than 0.02). No significant adverse effects occurred. Further study of the potential usefulness of GH in COPD utilizing a placebo-controlled trial is warranted.