Background: The appendix is a worm like extension of caecum and for this reason has been called "vermiform appendix". Appendicitis may occur due to several reasons, such as an infection of the appendix, but the most important is the obstruction of appendiceal lumen. Acute appendicitis has remained the most common acute surgical condition of the abdomen in all ages and of course, a common disease in surgical practice. The usual picture of appendicitis is often not classical, leaving in many cases a diagnostic problem. In patients with questionable findings, the aggressive surgical approach has been "when in doubt, take it out, "and the price paid is the frequent removal of normal appendix. Aim of the Work: The aim of the work is to evaluate the appendicitis inflammatory response (AIR) score and compare its performance in predicting the risk of appendicitis to the Alvarado score. Patients and Methods: In this randomized prospective study, 100 patients with acute pain in right lower quadrant of abdomen were admitted to the surgical department of Al-Hussain University Hospital in the period from June 2017 to October 2017. All the patients had indications for appendectomy. The present study was carried out among patients suffering from acute pain in right lower quadrant of abdomen. Results: This randomized prospective study comprised 100 patients, of whom 52 were females (52%) and 48 were males (48%). Their ages ranged from 16 to 42 years old with a mean age of 21 years. These 100 patients were presented with acute pain in right lower quadrant of abdomen. All female cases proved to be pregnant were excluded from the study. Recurrent sub-acute appendicitis were also excluded from the study. Patients with known abdominal malignancies or previous abdominal surgery were also excluded from the study. Conclusion: This prospective study comprised 100 patients with acute right iliac fossa pain for evaluation and comparing between Alvarado score and AIR score in diagnosis of acute appendicitis. The present study showed that the AIR score has a good statistical discrimination for patients with acute appendicitis and outperforms the Alvarado score.