Abstract: Appendicitis has been a cause of mortality through the history and has still remained as a major problem in spite of advances and improvements of medical sciences. Acute appendicitis is the most frequent cause of acute abdomen for the patients referring to hospitals. Patients will recover after a timely diagnosis and appendectomy. However, absence of timely and proper diagnosis may result harmful complications and even death. This descriptive-analytic retrospective study was carried out with the evaluation of medical records of those went to Shahid Beheshti and Yahyanejad hospitals from 2002-2004. The data was statistically analyzed by using SPSS software and chi-square and fisher's Exact statistical tests. Out of 1190 cases of non-perforated acute appendicitis, 64.3% were in 15-34 years age group, 727 patients were male and remaining were female, 121 patients with perforated appendicitis that had the highest frequency (49.5%) were in the age group 15-34 years (60 patients), 85 patients were male (70.2%). However, the highest perforated to non-perforated appendicitis ratio (21.5%/78.4%) belongs to the age group over 65. About 16.5% patients with perforated appendicitis were urban but 83.4% patients were rural, 74.3% of the121 cases of perforated appendicitis had occurred within the first half of the year and 25.6% within the second half. This study proved that incidence of perforated appendicitis is more common between rural patients and those who had referred to hospital in the first half of the year. So living in the village and first half of the year are two important risk factors for acute appendicitis.