Although antibiotic therapy seemed to be a safe treatment option for acute appendicitis, indications of this treatment have not been fully evaluated. We hypothesized that clinical and radiologic mild appendicitis may be a candidate for short-term antibiotic therapy. The purpose of present study was to examine the efficacy and the recurrence rate of short-term antibiotic therapy for consecutive patients with mild appendicitis. A prospective observational study was conducted over 3 years. The mild appendicitis was defined as the intermediate Alvarado score (4-8) and dilated appendix from 6 mm to 10 mm in radiologic study. All patients received initial antibiotics administration with clinical observation during 48 hours. The failure to respond to therapy and the incidence of recurrence were assessed. There were 107 enrolled patients with the mean Alvarado score of 6 ± 1 and the mean appendiceal diameter of 7.4 ± 1 mm. Of these, 97 (91%) exhibited improved symptoms and were discharged. The remaining 10 patients underwent surgery because of clinical aggravation, and pathology revealed true appendicitis in six of them. Of the 97 patients in whom the initial treatment was successful, five patients (5%) exhibited recurrent symptoms during a median follow-up period of 18 months. Of these five patients, three were treated with surgery (all true appendicitis), and the remaining two were once again treated with antibiotics. Patients with suspected appendicitis, those in whom mild appendicitis was diagnosed after clinical and radiologic evaluations, were found to benefit from short-term antibiotic therapy.