Eleven patients with severe necrotizing fasciitis involving the soft tissues and muscles of the perineum, abdominal wall, buttocks, and thighs were treated on the Tulane Surgical Service in New Orleans between 1979 and 1981. The etiologic factor in ten of these patients was a neglected or inadequately drained perirectal abscess. Three of the 11 patients died of the disease and ensuing multiple organ failure, for a mortality of 27%. All of the patients had signs of systemic sepsis. Initial radical debridement of all involved tissues, diverting colostomy, and aggressive medical support of the multisystem failure that ensues from sepsis are essential for successful management. To decrease the prohibitive mortality, early treatment is essential. A preventive measure appears to be operative drainage under adequate anesthesia of all perirectal abscesses.