The nature of the relationship of periodontal disease to a number of systemic health outcomes, including chronic obstructive pulmonary disease (COPD), remains unclear. Various causal mechanisms have been proposed to explain the observed epidemiologic associations between periodontal diseases and respiratory diseases. We have reviewed the epidemiologic and clinical evidence for this association. The methodologic approach we have taken is based on a structured systematic review of the indexed biomedical literature on these subjects. The primary focus of this review was on the analysis of periodontal health status measures and their association with COPD, which includes chronic bronchitis and emphysema. We found that a paucity of published results exist on this specific relationship and those which do exist typically represent secondary analyses of existing data sets. Nevertheless, the epidemiologic evidence identified in this systematic review indicates that worse periodontal health status is associated with an increased risk of COPD, with odds ratios ranging from 1.45 to 4.50 (significant at the 95% confidence interval). However, it is possible that residual confounding by tobacco smoking may account in part for the observations. A causal association between periodontal health status and risk of COPD, although biologically plausible, remains speculative. Randomized controlled trials will be required in order to address the question of causality and to better understand the biological basis of these epidemiologic associations.