This is a prospective study on 123 randomly selected patients admitted with the diagnosis of acute appendicitis. The value of rebound tenderness as a clinical diagnostic tool was statistically compared to those of some other physical signs; namely guarding, rigidity and Rovsing's sign. Rebound tenderness was found to carry the highest sensitivity (94.7%), negative predictive value (81.3%), reliability (49.1%), and association with histological diagnosis (P < 0.05). However, its specificity and positive predictive value was not significantly different from those of other physical signs. It is concluded that, in contradistinction to some previously published reports, our study emphasizes the role of rebound tenderness in the clinical diagnosis of acute appendicitis.