A total of 30 patients (aged 6-56 years) with nocardiosis and infection due to human immunodeficiency virus type 1 (HIV-1) were identified in our institution between January 1985 and June 1989. Eighteen patients had an AIDS-defining illness before or concurrently with nocardiosis. The mean CD4 lymphocyte count was 109/mm3. Pulmonary nocardiosis in 21 patients, extra-pulmonary nocardiosis in 8, and pulmonary and extrapulmonary nocardiosis in 1 patient was diagnosed. Chest radiographs showed alveolar patterns of infiltrates in 14 patients, reticulonodular patterns in 2, mixed alveolar and reticulonodular patterns in 6, cavitation in 4, and pleural effusion in 3. Of 27 patients treated, the conditions of 22 improved, but the extensive disease in 5 progressed. For 14 patients, recurrence was rapid after their treatment was discontinued. Nocardiosis caused or contributed to the death of 19 patients; in six patients, there was no evidence of nocardial infection at death. Nocardiosis can be a fatal complication of advanced HIV-1 disease. Delayed diagnosis, extensive disease, and early discontinuation of treatment were associated with poor outcome.