The authors report the radiographic findings in 13 cases of subphrenic abscess complicating abdominal operations at Severance Hospital, Yonsei Medical Center. Radiogaphic diagnosis is important because clinical feature may be masked when a patient is receiving antibiotic for presumed sepsis elsewhere. 1. There were 13 cases of subphrenic abscess after 670 abdominal operations (1.9%). 2. The post-operative subphrenic abscess incidence was 3.2% following gastrectomy, 2.9% after small bowel operations, 1,2% following cholecystectomy, 1.0% after appendectomy, and 1.3% each after operations on the colon and uterus. 3. the most common radiographic findings of subphrenic abscess were pleural effusion and elevation of diaphragm or decreased diaphragmatic movement during fluoroscopy; others include abnormal air shadow in abscess cavity, linear atelectasis in lung base, displacement of stomach fundus or colon. 4. There were 21 pleural effusion following 670 abdominal operations (3.1%), 0 of which occurred in patients subsequently proven by drainage to have a subphrenic abscess.