This prospective study comprises 651 patients with knife wounds of the anterior abdomen. Three hundred and forty-five patients (53%) had symptoms of an acute abdomen on admission and were operated on immediately. The remaining 306 patients (47%) were managed conservatively with serial clinical examinations. This group included 26 patients with omental or intestinal evisceration, 18 patients with air under the diaphragm, 12 patients with blood found on abdominal paracentesis, and 18 patients with shock on admission. Only 11 patients (3.6%) needed subsequent operation, and there was no mortality. The overall incidence of unnecessary laparotomies was 5% (completely negative, 3%). Of the 467 patients with proven peritoneal penetration, 27.6% had no significant intra-abdominal injury. It is concluded that many abdominal stab wounds can safely be managed without operation. The decision to operate or observe can be made exclusively on clinical criteria. Peritoneal penetration, air under the diaphragm, evisceration of omentum or bowel, blood found on abdominal paracentesis, and shock on admission are not absolute indications for surgery. Alcohol consumption by the patient does not interfere with the clinical assessment.