Objective The study investigated the epidemiology of Filifactor alocis (F. alocis) in subgingival plaque samples from subjects with different periodontal statuses. The relationship between the prevalence of F. alocis and clinical periodontal parameters was also analyzed.Methods Subgingival plaque samples and periodontal data were collected from 68 healthy sites (H groups) in 17 healthy subjects, 64 healthy (G-H group) and 76 diseased sites (G-D group) in 19 patients with chronic gingivitis, and 36 healthy (P-H group) and 56 diseased sites (P-D group) in 14 patients with chronic periodontitis. The plaque samples were analyzed by polymerase chain reaction, and possible correlations between the F. alocis detection rate and the bleeding index, probing depth, or clinical attachment level were determined.Results The detection levels of F. alocis increased in both healthy and diseased groups. The lowest level at 30.88% (21/68) was noted in the H group, whereas the highest level at 91.07% (51/56) was obtained from the P-D group. A significant correlation was found between the F. alocis detection levels and periodontal disease condition (PConclusion F. alocis was found at increased levels in subjects with periodontal disease. The presence of F. alocis increases the risk of sites with abnormal clinical periodontal parameters.