Objective The aim of this study was to investigate the prevalence of T.forsythensis in Chinese chronic periodontitis patients, and correlate it with clinical parameters. Methods 108 chronic periodontitis patients were selected according to clinical criteria. In each patient, subgingival plaque samples were collected from two of the periodontitis involved molar sites with the deepest periodontal pocket depth（diseased sites）and one healthy gingival sulcus （healthy sites）. T.forsythensis was detected by 16S rRNA polymerase chain reaction. Clinical assessments including probing depth, clinical attachment loss and bleeding on probing, were made at sampling sites. Results The prevalence of T.forsythensis in diseased sites and healthy sites was 59.72% and 3.70% respectively（P
