Many aspects of acquired immunodeficiency syndrome (AIDS) have been described in detail in the literature. However, there have been very few articles on the phenomenon of deep vein thrombosis (DVT) in the lower extremities of human immunodeficiency virus (HIV)/AIDS patients. The objective of this communication is to record the incidence of DVT in HIV/AIDS patients and the risks for development of embolic events and to emphasize the need for prevention and for the vigorous treatment of this complication. We conducted a retrospective review of HIV/AIDS-infected patients with DVT admitted to Mount Sinai School of Medicine/Cabrini Hospital in New York during the last 5 years. Analysis includes demographic data; risk factors for HIV/AIDS infection; associated medical problems; recent surgery; and laboratory findings including CD4 counts, platelet counts, prothrombin times, partial thromboplastin times, and plasma albumin levels; and image studies. From January 1995 to January 2000 4752 HIV/AIDS-infected patients were admitted. Of those admitted to the hospital 45 (0.95%) were found to have DVT. There were 36 males and nine females (mean age 43 years). Of the 45 patients 38 had infectious complications and 13 developed a malignancy. The distribution of the thromboses were the femoral vein in 23 patients, the popliteal vein in 20 patients, and the iliofemoral system in 2 patients. Twelve patients had recurrent DVT and three patients developed a pulmonary embolism. HIV/AIDS infection is a considerable risk for development of DVT in the lower extremity. Statistically DVT in HIV/AIDS is approximately 10 times greater than in the general population. Emphasis upon prevention and vigorous treatment of DVT is recommended.