It is known that gas gangrene demands a prompt treatment immediately after the onset of the disease and it has a poor prognosis when it affects aged patients or the trunk. We experienced a successfelly saved case of gas gangrene extended from both hips to pararectal space in a 78-year-old man. The patinet was seen at another hospital because of a high fever (40°C). No symptomatic remission was attained and the patient was referred to the hospital. He had an underlying disease of prostatic hypertrophy which was diagnosed in 1985. Five days after admission, redness with sever pain and induration appeared in the left hip, and on the next day skin of the left hip became necrotic. Plane X-ray film and CT scan of the lower abdomen revealed gas in both hips and pararectal space. Based on these findings the patient was diagnosed as gas gangrene, and immediately colostomy and aggressive resection of necrotic tissue were performed. The pararectal space was drained and subsequently washed with oxydol everyday until 62 days after the operation. The patient made a full recovery.