The objective of the study is to examine the reliability of the cough sign in order to diagnose acute appendicitis in adult patients, comparied to four other commonly used tests. Methods: We conducted a prospective clinical trial of I H2 consecutive patients referred to our university-based emergency department within the study period Adult patients with the chief complaint of acute-onset non-traumatic right lower quadrant abdominal pain were enrolled in the study Cough sign, rebound tenderness, right lower quadrant tenderness, guarding and percussion tenderness were sought on examination. Specificity, sensitivity, negative and positive predictive values of the five tests in diagnosing acute appendicitis were calculated Results: Fifty/one out of the 182 patients had a presumptive diagnosis of acute appendicitis and 4-1 were found to halve acute appendicitis. Positive cough sign was found to be the most sensitivity examination method (95% in general). The negative predictive value of the test was also the highest among the five tests in our study (9H%). Percussion tenderness was the most specific method. Rebound tenderness had the highest positive predictive value of the five tests. Conclusion: We conclude that the cough sign can serve as a useful aid in establishing the diagnosis in acute appendicitis in the emergency department evaluation of adult patients with non-traumatic, acute-onset right lower quadrant abdominal pain.