Objective: Recent reports have shown an association between periodontitis and chronic obstructive pulmonary disease (COPD). Our objective was to assess the subgingival microfl ora in relation to COPD status. Methods: Eighteen subjects were classifi ed into four different groups according to clinical periodontal status and the diagnosis of COPD. DNA from subgingival plaque samples was extracted and the bacterial 16S rRNA genes were PCR amplifi ed, cloned, and sequenced to determine species identity. Results: From a total of 1041 clones, 168 species or phylotypes were detected. Higher amounts of Actinomyces spp., Veillonella spp., and Campylobacter gracilis were detected in the subgingival microfl ora of periodontally healthy COPD subjects, as compared with controls. COPD status was found to have little infl uence on the subgingival microfl ora in periodontitis subjects. Conclusion: COPD status does seem to infl uence the healthy but not the diseased subgingival microfl ora in periodontitis. Although preliminary, these fi ndings indicate that there may be host factors responsible for the increased susceptibility of COPD subjects to periodontal disease.