This is the first case report ofClostridium septicumsepticemia in a patient with large granular lymphocyte leukemia. C. septicuminfection is highly associated with malignancy and causes a rapidly fatal enterocolitis among patients who are profoundly neutropenic. The need for early recognition and Combination of early antibiotic therapy and necessary surgical intervention may help to alter the fulminating nature ofC. septicuminfection.