a prospective study wa undertaken in the surgical unit of HMC, Peshawar to test the efficacy of modified alvarado scoring system in the diagnosis of acute appendicitis. The study lasted for six months, between May 2001 and Oct. 2001. all those adult patients who were amditted with abdominal pain suggestive of acute appendicitis and were assigned a score according to modified alvarado score were included in the study. Patients who were either not assigned a score or were under 12 years of age were not included in the study. Out of the 90 patients, the males were twice (n = 60) as common as females (n = 30). Age group most commonly affected was 21 to 30 years. Teh results revealed a positive predictive value of 88% in all and even more so in case of male patients. it is concluded that this scoring system is an effective tool in the diagnosis of acute appendicitis in adult especially male patients and is very helpful for the young doctor whose clinical judgement does not match that of a senior colleague.