In this study, a new sign for clinical diagnosis of acute appendicitis is introduced. The study was performed on a sample of 250 cases simply selected from the patients with acute appendicitis admitted to Al-Zahra Hospital of Isfahan. Before operation, the patients were evaluated for this sign in order to. assess its predictive value in diagnosis of acute appendicitis. Following the intervention, the appendix was sent to the department of pathology to confirm the diagnosis. Abdominal examinations prior to operation included checking the superficial and deep tenderness, rebound tenderness, Rovsing and the new sign. To check the new sign, while the patient was lying in a supine position, then the physician places his left hand below the right costovertebral angle and inflicts a few short thrusts on the flank. In case, the patient feels pain in front of the lower abdomen, and with his/her hand locates the pain, it will be considered as a positive sign. Then predictive value, sensitivity and specificity of the new sign in diagnosing acute appendicitis were assessed. For comparison of the qualitative variables chi-test and for the quantitative variables Hest were employed. The results showed that sensitivity of the new sign is 67%, its specificity is 35%, its negative predictive value is 32% and its positive predictive value is 72%. This new sign here after named (BEHDAD SIGN) can, along with other signs, helps to diagnose acute appendicitis.