We determined the effect of age on the restoration of lost body weight and lean mass after burn injury, using the anabolic steroid oxandrolone. Patients with deep burns of 30-55% of body surface were studied when entering the recovery phase of injury, defined as resolution of the hypermetabolic, catabolic state. Patients were provided optimum nutrition and exercise alone or with the addition of oxandrolone. The rate of body weight and lean mass gain and improvement in physical function were measured over a 4-week period. Four groups were studied. A younger group, mean age of 34 years and burn size of 47+/-7% versus an older group, mean age 60 years and burn size 36+/-5%. The mean loss of body weight in the younger and older groups was 10+/-2 and 11+/-2% of total. Both groups were randomly divided into a control and oxandrolone study group. Weight restoration, 74+/-5% of which was lean mass, averaged 1.7+/-0.4 kg and 1.6+/-0.3 kg per week in the young and older oxandrolone groups. This rate was compared with 0.7+/-0.2 kg and 0.5+/-0.2 kg in the young and older control groups, with only 55% of weight gain being lean mass. These differences were statistically significant. The increase in the rate of weight gain with oxandrolone corresponded with a 30% decrease in length of stay in the burn rehabilitation unit. We concluded that the ability of an anabolic steroid to restore lean mass and physical function after burn surgery is not related to age.