The purpose of this study was to assess the clinical and microbiological effect of chlorhexidine rinse and supragingival plaque control following scaling and root planing on adult periodontal disease. 14 patients with adult periodontitis were selected for the study . They had not taken antibiotics for 6 months and history of dental treatment for 6 months before the study. Patients received a supragingival scaling and root planing under local anesthesia, plaque control group was subjected to professional plaque control 2 times for a period 2 week, chlorhexidine rinse group were subjected to twice daily 0.2% chlorhexidine rinse for a period 2 week. Clinical examination (plaque index, gingival index, probing pocket depth) and distribution of the bacteria morphology of subgingival plaque were monitored on baseline (0 week), 1 week, 2 week, 4 week and 6 week. The results were as follows : 1. Plaque index in chlorhexidine rinse group , plaque control group and control group was significantly reduced during all weeks (P<0.05). 2. Probing pocket depth was significantly reduced at 2, 4, 6 week (P<0.05) in chlorhexidine rinse group and control group, plaque control group was significantly reduced during all weeks (P<0.05). 3. Gingival index was significantly improved at 2, 4, 6 weeks(P<0.05) in chlorhexidine group and plaque control group, control group was significantly improved at 1, 2, 4 weeks (P<0.05). 4. Percentage of cocci was significantly increased at 1, 2, 4 and 6 weeks in chlorhexidine rinse group and control group, plaque control group was significantly increased at 2, 4 and 6 weeks(P<0.05). 5. Percentage of non-motile rods in all group were not significantly changed when compared with those of baseline (0 week) (P<0.05). 6. Percentage of motile rods was significantly reduced during all weeks (P<0.05) in chlorhexidine rinse group, plaque control group was significantly reduced at 2, 4, 6 weeks and 1, 2 and 4 weeks in control group. 7. Percentage of spirochetes was significantly reduced during all weeks (P<0.05), plaque control group was significantly reduced at 2, 4, 6 weeks and 1, 2, 4 weeks in control group. This results were suggested that clinical and microbiological effect of chlorhexidine rinse and supragingival plaque control following scaling and root planing on periodontal disease