In 81 patients with acute abdominal pain, laparoscopy was performed because of diagnostic doubt. Diagnosis by clinical methods proved to be correct in 42 of the patients and laparoscopy gave correct diagnosis in 70. Appendectomy revealed acute appendicitis in 19 patients and normal appendix in five. Failure to establish a diagnosis by laparoscopy was due to incomplete visualization of appendix in nine patients, pelvic adhesions in one patient, and failure to enter the peritoneal cavity in another. A clinical diagnosis of acute appendicitis could be invalidated by laparoscopy in 17 of 40 patients. Negative laparotomy is potentially avoidable by use of laparoscopy when a diagnosis of appendicitis is questionable. Laparoscopy may therefore be warrantable in such cases.