There were a lot of reports about the pathogens of tonsillitis and sinusitis, but there were few reports in the comparison of microbiological study of sinus, nasopharynx and middle meatus. So authors had studied for 64 children undergoing tonsillectomy and adenoidectomy from March 1992 to February 1993 to determine the microbiological difference of the tonsil surface, tonsil core, adenoid, middle meatus & maxillary sinus. The results were as follows ; 1) The range of age was 4 to 15 years old and sex incidence was 38 males(59.4%) and 26 females(40.6%). 2) In all of the culture site, the most predominant microbial organism was nonpathogenic neisseria. 3) In the comparison of microorganism of each culture sites, high correlation rates were found between middle meatus and maxillary sinus(57.8%) and between tonsil surface and tonsil core(51.6%). 4) The rate of no growth was the highest in maxillary sinus(23.4%). Most of the cases were with single infection, but the incidence of mixed infection was 6.3% in tonsil surface, and 3.1% in tonsil core and adenoid. 5) Aerobes were isolated in most of the cases and in only 2 cases, anaerobes were isolated. 6) In normal sinus group, most of the cases(75%) showed no organisms in culture. But in diseased sinuses, organisms were cultured in all the case.