Rhodococcus equi, a facultative intracellular bacterium, is a common cause of pulmonary infection in farm animals, especially foals. Pulmonary and disseminated infection caused by this organism is occasionally seen in humans, especially in patients whose cell-mediated immunity has been altered by glucocorticoids or cytotoxic chemotherapy. Not surprisingly, the organism may cause serious disease in human immunodeficiency virus (HIV)-infected humans whose T cell-dependent immune system has been profoundly suppressed. This report describes an HIV infected patient with Rhodococcus equi pneumonia and reviews nine additional HIV-infected patients. Treatment in humans is not standardized. Studies in foals indicate that erythromycin and rifampin together are the treatment of choice. The patient in this report responded to this treatment briefly before relapsing and dying of the infection.