Backgrounds: Acute otitis media (AOM) is a common childhood infection that is frequently treated by antibiotics. There are no prospective and comprehensive trials evaluating childhood AOM for etiologic pathogens and resistance pattern in Turkey. The aims of the study were to determine the bacterial etiologies and resistance patterns, and identify the efficacy and the relapse rates of 3 days of azitromycin and 10 days of cefaclor therapy in AOM. Methods: This prospective, randomized, single-blind, open study was carried out in 78 cases of AOM. Mean age was 30.7 +/- 27 months. Tympanocentesis and aspiration of middle ear fluid (MEF) were used to obtain purulent material from the middle ear. Group 1 consisted of the cases (n = 41) on azitromycin therapy and Group 2 (n = 37) on cefaclor. Dosage of azitromycin was 10 mg/kg per day for 3 days and cefaclor 40 mg/kg per day for 10 days. The patients were evaluated on days 3-5 (second visit), day 10 (third visit), and day 30 (fourth visit) during follow-up. Results: A total of 50 species were isolated from 44 of 78 cases from which materials were obtained (44/78; 56.4%). Most frequently isolated microorganism was Streptococcus pneumoniae (n = 18; 36%), followed by Haemophilus influenzae (n = 11; 22%), S. aureus (n = 9; 18%), Moraxella catarrhalis (n = 4; 8%), and group A beta-hemolytic streptococcus (GAS, n = 4; 8%). Enterococcus faecalis was isolated from three cases and H. parainfluenzae from one. Penicillin and amoxicillin resistances of bacteria were found to be 40 and 36%, respectively. The frequency of penicillin and amoxicillin resistance in less than or equal to24-month age group was 59 and 66.6%, respectively. The patients did not demonstrate significant differences in terms of cure rate on the third to fifth day (Group 1: 32.5%; Group 2: 36.4%), 10th day (Group 1: 76.9%; Group 2: 84.8%), and on 30th day (Group 1: 91.3%; Group 2: 81.8%). There were no significant differences with respect to side effects, relapse, and re-infection rate between the two groups. Conclusion: In more than half of the AOM cases, bacteria were isolated from MEF and most frequently isolated organisms were S. pneumoniae, H. influenzae, and S. aureus. Three-day azitromycin therapy was as effective as 10-day cefaclor therapy. (C) 2002 Elsevier Science Ireland Ltd. All rights reserved.