Acute appendicitis is one of the most common surgical disease and differential diagnosis with many other disease is necessary. Mensturation, pregnancy, and other gynecological diseases during reproductive age in female sometimes cause difficulties in differential diagnosis of acute appendicitis and therefore leads to high percentage of misdiagnosis. Two hundred of women in there reproductive ages who had operation for acute appendicitis during the time period of three years in the department of surgery, Yonsei University medical center, were the subjects of study; their histories were reviewed in order to analyze the possible factors that might be necessory in differential diagnosis of acute appendicitis. Following results came out 1) 70% Of the women whose histories were reviewed were in their reproductive ages; among them 56% were in the twenties. 2) 5 2.5% of the patients were admitted within 24 hours after the initial onset of symptoms and as the time is delayed, worsening of histopathological finding and the incidence of misdiagnosis increased. 3) Increase in WBC count was present in 61.5%,' of the cases and it was significant in diagnosis of acute appendicitis. 4) The most common symptom was right lower quadrant abdominal pain(85%) followed by anorexia, indigestion, nausea and vomiting in descending orders of frequency, and the most common sign was right lower quadrant abdominal tenderness, both direct (87%) and indir ect(42%) 5) In 69.8% of the cases, it was possible to confirm certain evidence of inflammation histopathologically. Acute suppurative and gangrenous inflammation was the most common histopathological finding comprising 39.5% of all cases. 6) There were no differences in incidence depending on menstrual phases, but the chance of misdiagnosis and the severity were higher during the follicular phase compared to luteal phase. 7) The average hospital day were 4.4 in non-perforated appendicitis and 10 in perforated ones. 8) Complications were present in 7.7% of all cases.