The aim of this study was to determine the feasibility, tolerance, and efficacy of enteral feeding in malnourished AIDS patients. This was a prospective study of eight AIDS patients with severe eating disorders associated with systemic diseases. A defined diet was administered through an endoscopically placed gastrostomy tube. Body composition studies and selected serum and immunologic studies were done at baseline and monthly for 2 mo. Enteral feeding was associated with an increase of approximately 14% in total body potassium, an index of body cell mass (P less than 0.02), and an increase in body fat content (P less than 0.002). Serum albumin concentration (P less than 0.005) and iron-binding capacity also rose. Serum immunoglobulins did not change. The numbers of total lymphocytes (P less than 0.005) and CD8+ cells rose but CD4+ cells did not change. The tube and enteral feedings were well tolerated. These results demonstrate that enteral feeding may result in body-cell-mass repletion in malnourished AIDS patients.