This study was designed to compare the Antimicrobial effect of the several antibiotics on anaerobes. After Bacteroides gingivalis was streaked on the surface of Blood agar plates, antibiotic discs were applied and cultured 5 days anaerobically. Following results were obtained 1. All of the examined antibiotics had antimicrobial activity with varying degree. 2. The antimicrobial activity of Clindamycin and Tetracycline was larger than any other antibiotics. Vancomycin showed the lowest activity. Erythromycin and Ampicillin showed the moderate antimicrobial activity. (P<0.05)