PURPOSE: The purpose of this study is to confirm the clinical usefulness of the Alvarado score's application and the differences in diagnostic values between male and female for patients who were diagnosed with acute appendicitis when they came to the hospital for pain in the right lower abdomen. METHODS: The subjects of this study were 211 patients who entered the surgical department of this hospital for doubtful acute appendicitis from June 2003 to May 2005. Using a retrospective method, we examined the patients' records and compared their ages, sex, symptoms, preoperative physical examinations, leukocyte and neutrophils figures, and the final postoperative pathological diagnosis. RESULTS: One hundred twelve patients were male, and 99 were female. A clinical Alvarado score of above 7 in sensitivity, specificity, positive predictive value, and negative predictive value was the standard for being judged positive. In this study, the sensitivity of the Alvarado score was 86.2%, its specificity was 61.6%, and the accuracy of diagnosis was 82.9%. The positive predictive value was 92.6%, and the negative predictive value was 51.0%. The accuracies were 83.9% and 81.8%, respectively, that for males being a little higher than that for female, but with no statistically significant differences. CONCLUSIONS: This study showed that the diagnosis of acute appendicitis was highly accurate for an Alvarado score above 7 (82.9%). The diagnosis of acute appendicitis by using the Alvarado score is simple, fast, reliable, and repeatable, and it can be used under any conditions without other expensive and complicated diagnostic tools.