Over the last decade the acquired immunodeficiency syndrome (AIDS) has become one of the leading causes of morbidity and mortality both in Europe and the United States. The disease is due to infection by the human immunodeficiency virus (HIV), which results in progressive loss of cellular immunity; consequently, patients are susceptible to both typical infections with high-grade pathogens and also low-grade opportunistic organisms. In addition, different cancers such as Kaposi's sarcoma and non-Hodgkin's lymphoma occur with increased frequency. Nuclear medicine has a central role to play in the diagnosis of these malignant and infectious conditions. This article reviews the role of radionuclide studies in the diagnosis of HIV-related disease.