Background and objective: Abdominal ultrasound can provide an effective, non-invasive, fast, inexpensive, and safe procedure with no risk of radiation to patients. Accordingly, this study aimed to assess the role of ultrasonography in differentiating causes of right iliac fossa pain among patients admitted to emergency hospitals in Erbil City. Methods: In this cross-sectional study, 120 patients with acute abdominal pain and tenderness of right lower quadrant (iliac fossa) region, clinically suspected to have acute appendicitis admitted to the emergency hospitals in Erbil city were included in the study, from April 2011 to February 2012. The data was collected through a direct interview of patients, followed by a sonographic examination. Results: The prevalence of true positive sonographic examination was 60.8%, with only 30% true negative findings. Around 69% of the cases had acute appendicitis, followed by ovarian cyst and right ureteric stone (11.1% and 7.4%, respectively). The sensitivity of sonographic examination in identifying appendicitis was 90.1%, the specificity was 92.3%. The positive predictive was 96%, while the negative predictive value was 81.8%. Sonographic characteristics of the positive patients with appendicitis showed that 58.0% of the patients had swollen appendix, and a diameter of 7.1-8 mm was the most imaging finding. Also, appendicitis was significantly (P = 0.02) more common (58%) in males, and negative appendectomy was prevalent among females. Conclusion: Appendicitis was the major cause of the right iliac fossa pain. Abdominal ultrasound was a reliable method in the diagnosis of the majority of patients with right iliac fossa pain and can decrease the rate of negative appendectomy.