The Swiss HIV Cohort Study (SHCS) is a prospective cohort study of HIV-infected adolescents and adults seen at 7 outpatient clinics (Swiss University Hospitals in Basle, Berne, Geneva, Lausanne, Zurich, the St. Gall Cantonal Hospital and the Civico Hospital in Lugano). The SHCS serves as an infrastructure for different research projects and includes about 70% of all patients with advanced disease in Switzerland. From April 1984 to November 1995 3120 HIV-infected patients of the SHCS died. Autopsies were performed in 314 of these patients. The aim of our study is to analyse autopsy findings as well as causes of death in those 314 HIV-infected patients. An HIV-related cause of death was found in 271 (86%) of the patients, 12 patients (4%) died of a drug overdose, and 3 (1%) of the patients committed suicide. 28 (9%) died either from an HIV unrelated or unidentified cause. The five most frequent causes of death were: bacterial pneumonia (52 patients, 17%), Pneumocystis carinii pneumonia (40 patients, 13%), lymphoma (34 patients, 11%), cytomegalovirus infection (33 patients, 11%), and toxoplasmosis (30 patients, 10%). During our study marked progress occurred in treating HIV-infected patients and preventing opportunistic infections. These improvements have further changed the natural course of acquired immunodeficiency syndrome. They are reflected in the falling rate of Pneumocystis carinii pneumonia and toxoplasmosis, as well as an increase in lymphoma as a cause of death over the period of our study.