Untreated gas gangrene is a fulminating infection that can lead to extensive tissue necrosis and death. Hyperbaric oxygen, when used with antibiotics and surgical debridement, can lead to decreased mortality. Nine patients with gas gangrene proven by positive clostridial cultures have been treated at St Luke's Hospital of Kansas City with a mortality of 11.1%. A case of gas gangrene developing from a perirectal abscess is presented.