We have collected 62 cases of post-operative subphrenic abscess. Two thirds of these patients were sent to us by another unit for post-operative complications. Subphrenic asbcess is still very dangerous as the mortality is still 38%. They occurred after a gastro-duodenal operation (26 times), spleno-pancreatic operation (21 times), intestinal operation (15 times), hepato-bilary operation (11 times) appendicectomy (twice). They were situated usually on the right, but 11 patients had a double subphrenic abscess and 14 an associated submesocolic abscess. Gram negative bacteria were usually the cause. These abscesses often started early. They occurred in 80% of cases in patients operated under the antibiotic cover. Chest X-ray was the best method of detection, but experience is necessary to read them. The abscesses were drained by the abdominal route in order to verify th whole peritoneal cavity. 22 patients died. 11 from septicemia. 21 out of 22 had a digestive fistula. Among the factors in prognosis, the most obvious were age, type of operation, the notion of reoperation, multiple abscess, and finally the delay in starting treatment.