The 16S rRNA analyzing method is a bacterial identification method that is useful in identifying bacteria which is difficult to do by other means. The following 7 types of bacteria which are Treponema, A. actinomycetemcomitans, P. gingivalis, Fusobacterium, B. forsythus, P. intermedia, P. micros were evaluated in order to study their distribution among patients with adult periodontitis. The 16S rRNA analyzing method was used to compare bacterial distribution among 3 groups. Subgingival plaque acquired from the affected sites(pocket depth ${geq}6mm$) of 29 patients with adult periodontitis were grouped as the experimental group while plaque from the non-affected sites(pocket depth ${leq}3mm$) were grouped as control 2 and finally plaque acquired from students with healthy periodontal tissues were grouped as control 1. The results are as follows ; 1. The distribution of Treponema was 12.5% for control 1, 21.4% for control 2 and 75.4% for the experimental group. For A. actinomycetemcomitans the distribution was 0.5%, 19.0%, 44.4% in respect to the order of groups mentioned above. P.gingivalis showed 10.5%, 43.1%, 94.0% distribution, Fusobacterium 33.0%, 48.3%, 81.0% distribution, B. forsythus 9.5%, 17.2%, 65.9% distribution, P. intermedia 1.0%, 12.1%, 26.3% distribution and finally P. micros 5.0%, 19.0%, 48.7% respectively. In all 7 types of bacteria, the experimental group showed higher bacterial distribution compared to the other two groups with statistically significant difference. 2. In the case of Treponema, A. actinomycetemcomitans, gingivalis,Fusobacterium, B. forsythus, P. intermedia, P. micros showed significant difference between control 1 and 2. These results suggest that the 16S rRNA analyzing method which was applied on Koreans for the first time could be utilized and useful in finding potential pathogens of periodontal disease.