A skin rash in marrow graft recipients often poses difficult diagnostic problems because multiple causes may be implicated, and clinical and histopathologic findings may be nonspecific. Five recipients of allogeneic bone marrow transplants had pityrosporum folliculitis diagnosed by skin biopsy in the early weeks (less than 18 days) after transplantation. In all cases, patients were febrile and leukopenic (granulocyte count, less than 500 cells/mm3), and were receiving broad-spectrum antibiotics at onset of the skin rash. Erythematous macules and papules were distributed primarily over the chest, shoulders, and upper back, and pustules and crusts developed in some cases. Granulocyte counts of more than 500 cells/mm3 were associated with resolution of the rash. Pityrosporum infection should be considered in the differential diagnosis of skin rashes in marrow graft recipients.