We report a case of nodular granulomatous Pneumocystis carinii pneumonia following bone marrow transplantation. The patient was a 40-year-old man who had undergone bone marrow transplantation for myeloblastic acute leukemia. He presented with fever, dyspnea and bilateral diffuse nodular infiltration of the lungs. Bronchoalveolar lavage was negative. Open lung biopsy was performed. Histological examination revealed a granulomatous reaction with central necrosis surrounded by epithelioid and giant cells. Toluidine blue and Gomori-Grocott stains identified a few P. carinii. Mycobacterial and fungal cultures were negative. A granulomatous reaction is rarely observed and almost only in HIV-infected patients. To our knowledge this is the first description in a bone marrow transplant recipient.