Wasting (malnutrition) and lipodystrophy are the two major nutritional alterations in human immunodeficiency virus (HIV)-infected individuals. Both wasting and lipodystrophy may involve a decrease in body fat content, while wasting-but not lipodystrophy-also includes the loss of lean body mass. Lipodystrophy has made the identification of wasting increasingly more difficult. The diagnosis of wasting depends on a definition of the condition that takes into account sex and cultural differences, as well as measurements of body cell mass. Patient management involves a concurrent, comprehensive approach designed to restore lost body cell mass and weight. The authors make recommendations for defining, diagnosing, and treating HIV-associated wasting. Specific therapies include testosterone replacement, other anabolic steroids, and recombinant human growth hormone. Other adjunctive measures, such as progressive resistance exercise and cytokine modulation, may also be utilized. Expected outcomes from effective treatment include restored body cell mass, improvement in quality of life, and reduced rates of hospitalization. Future directions for research should address the need for optimal treatment strategies.