Twenty-two children with severe protein-energy malnutrition were randomly assigned to dietary treatments that permitted either moderate (4-6 g.kg-1.d-1) rates of weight gain (MG, n = 11) or rapid (12-16 g.kg-1.d-1) rates of weight gain (RG, n = 11) to test the hypothesis that restoration of weight deficits by the RG group restores reference body composition. Final total body water was 60 +/- 4% of body weight in the MG group and 62 +/- 3% in the RG group (NS) indicating reference body composition was attained by both groups. Composition of weight gained was measured by energy and nitrogen balance from doubly labeled water and metabolic collection data. In early recovery, the percent (+/- SEM) protein, fat, and water in weight gain was 20 +/- 1%, 40 +/- 8%, and 40 +/- 10% in the MG group and 14 +/- 1%, 43 +/- 4%, and 43 +/- 12% in the RG group. In late recovery these were 13 +/- 1%, 42 +/- 7%, and 47 +/- 14% in the MG group and 12 +/- 1%, 46 +/- 4%, and 42 +/- 6% in the RG group. We conclude that the nutritional therapy used to promote rapid weight gain restores reference body composition and significantly reduces time required for catch-up growth.