The purpose of the research is to compare the distribution of Black-pigmented Bacteroides between Chronic Periodontitis and Aggressive Periodontitis. P. gingivalis, P. intermedia and P. nigrescens were examined in order to evaluate their distribution in patients with Chronic Periodontitis(CP) and Aggressive Periodontitis(AP). PCR and dot-blots hybridization of 16s rRNA gene were used to compare bacterial distribution of two groups - CP group and AP group, which were divided into two subgroups. Subgingival plaque taken from the diseased sites(pocket $depth{geq}6$ mm) and healthy sites(pocket $depth{leq}3$ mm) were grouped into the experimental group and the control group. The result are as follows ; 1. The distribution of P. gingivalis was 98.33% for chronic Periodotitis(CP), 94.17% for Aggressive Periodontitis(AP), the distribution of P. intermedia was 77.50% for CP, 64.17% for AP, and the distribution of P. nigrescens was 35.00%, 29.17%. In all 3 types of bacteria, CP group showed higher distribution compared to AP group, but only P. intermedia showed statistically significant difference. 2. In the case of CP, every type of bacteria showed higher distribution in the experimental group with statistically significant difference. 3. In the case of AP, every type of bacteria also showed higher distribution in the experimental group, but P. gingivalis and p..intermedia showed the result with statistically significant difference, and the other did not 4. In 3 all bacteria type, N-AP showed higher distribution than N-CP without statistically significant difference These results suggest that the comparison of the distribution of Bacteroides between Chronic Periodontitis and Aggressive Periodontitis has no statistically significant difference, except P. intermedia.