A brain abscess caused by a new variety of Cladosporium trichoides occurred in a previously healthy man. A reversed T-suppressor/helper cell ratio was noted as the only immunologic abnormality. He required three surgical procedures, the last an occipital lobectomy, and antifungal chemotherapy to control his disease. He received 2,068 mg of amphotericin B and one year of flucytosine at 6 g per day. Ten months after the last surgery he is without evidence of disease. C. trichoides var. chlamydosporum was isolated from the abscess. It differed from C. trichoides by producing chlamydospores in vitro and only hyphae in the brain abscess. On modified Sabouraud agar, the fungus did not grow at 25 degrees C and grew poorly at 30 degrees C and 37 degrees C. Histologic sections revealed necrosis, no encapsulation, and no epitheliod cells.