PURPOSE: To determine the frequency with which ultrasonography (US) provides a correct diagnosis and suggests appropriate guidance for the treatment of patients with right lower quadrant abdominal pain. MATERIALS AND METHODS: During an 11-month period, US was consecutively performed in 84 patients who were presented with right lower quadrant abdominal pain. In the 76 [M ; F=16 ; 60, age range 14 -87 (mean, 41) years] who formed the study population, final diagnoses were made surgically or clinically. For US, a 5 -7-MHz convex-array, 4-MHz vector-array, and/or 7-MHz linear-array transducer was used, according to the patient 's body habitus. To determine how often our US reports had provided a correct diagnosis and suggested appropriate guidance for surgical or medical treatment, and to calculate their diagnostic value, the reports were retrospectively compared with final diagnoses. RESULTS: US diagnoses were acute appendicitis in 40 patients (53%), diseases other than this in 25 patients (33%), and no abnormality in 11 (14%). In 38 of the 40 patients (95%), the diagnosis of acute appendicitis was surgically confirmed as correct, and for other diseases, diagnoses based on the findings of US proved to be correct in 21 of 25 patients (84%). Overall, diagnosis was correct in 67 (88%). As regards appropriate guidance for treatment, 46 (61%) and 30 (39%) patients were diagnosed by US to have surgical and medical diseases, respectively. In 44 of the 46 (96%), it was confirmed guidance was appropriate, and for the 30 with medical disease, this was so in all but one case (97%). Overall, the treatment plan was appropriate in 72 patients (95%). CONCLUSION: Our study revealed that US was able to provide a correct diagnosis in 88% of patients with right lower quadrant abdominal pain, and in 95% of these, the treatment plan suggested was appropriate. US is, therefore, a valuable screening tool in the diagnosis and therapeutic guidance of such patients.