This expe띠nent was performed to evaluate the contamination of private dental clinics and the effect of antiseptics. 까lere are high risks of cross infection in dental clinic during the dental treatffient both in dental clinic workers and dental pa디ents. We took the samples in 30 dental clinics. 4 sites(hand piece, head rest, room air, and cuspidor) were sampled in each clinic. Each samples were studied with molecular biologically using DNA sequencing. After DNA sequencing, all microorganisms were tested with 4 commercial antiseptics. The results were as followings. 1. 30 species and 54 strains of pathogenic microorga띠sms were found in 30 dental cωúcs. 2. 깨ere were no signifìcant difference in regions for fmding the micr，∞rganisms(p(O. 06). 3. 8 species and 13 sσains of micr∞rganisms were found in room air of Seoul area, and 6 species and 10 strains were in head rest of An-yang area were the most frequent sites. 4. Staphylococcus epidermidis was found the most frequently. 5. Calymatobacterium granulomatis and Enterococcus faecalis were found, which were not concemed with oral disease 6. Sterilization effect showed difference by antiseptics and also showed difference by sterilization method and sites. From the aboving resutls, there were no significant difference in regions for finding microorganisms, but little differences in sampling site. There were quite differences depend on the sterilization method and antiseptic drugs. It may be exist that there are high risks of cross contamination between dental c뼈c workers and patient.