The dematiaceous fungi appear to be an increasing cause of human disease. At The Methodist Hospital, in Houston, Texas, five cases of serious disease caused by these fungi occurred between 1987 and 1992. Cerebral abscesses with Xylohypha bantiana followed treatment for lymphoma. An infection of the lower extremity with Exophiala jeanselmei var. castellanii followed cardiac surgery. Peritoneal growth of Alternaria tenuissima was a complication of peritoneal dialysis. Cerebral abscesses with Dactylaria gallopava occurred in a liver transplantation patient. A traumatic ankle wound contaminated with dirt led to an infection with Phialophora repens. All patients except the last were immunocompromised at the time of the infection; diabetics and patients on steroids may be at particular risk.