In this article, we describe pulmonary hypertension in two men (31 and 43 years of age) with human immunodeficiency virus (HIV) infection who were examined at Mayo Clinic Rochester. Among 88 reported cases (including the two current ones) of HIV- or acquired immunodeficiency syndrome (AIDS)-associated pulmonary hypertension, 61% were male; the age range was 2 to 56 years (mean, 32). Dyspnea was the usual initial symptom. Of the 74 patients in whom pulmonary artery pressure was recorded or calculated by echocardiography, systolic pressures ranged from 49 to 118 mm Hg (mean, 68). Of the 33 cases in which lung tissue was evaluated microscopically, 28 (85%) were of the plexogenic variant of pulmonary arterial hypertension. Of the other five cases examined histologically, three consisted of thrombotic pulmonary arteriopathy (one was due to recurrent thromboembolism, and the other two were due to in situ thrombosis), and two were of pulmonary venoocclusive disease. No correlation existed between either CD4 counts or a history of pulmonary infections and the development of pulmonary hypertension. In 15 of the 88 patients (17%), confounding factors for hypertensive pulmonary vascular disease were present, including coexisting liver disease in 13 and coagulation abnormalities in 2. In 83% of the patients, the development of pulmonary hypertension seems to have been related primarily to the chronic HIV infection. Pulmonary hypertension was more rapidly progressive in patients with HIV or AIDS than in those with primary pulmonary hypertension; the reported time intervals between onset of symptoms and diagnosis were 6 months and 30 months, respectively. The 1-year survival rate for patients with HIV and pulmonary hypertension was 51%, based on the follow-up data compiled from the 63 patients in whom it was described; this compares with a 1-year survival rate of 68% for patients with primary pulmonary hypertension. Death was considered a direct consequence of pulmonary hypertension in 29 (76%) of the 38 fatal cases.