Systemic health is often closely linked to the state of the oral cavity: many systemic diseases and conditions have oral manifestations. Likewise, oral microbiological infections may also affect one's general health status. Indeed, animal and population-based studies now suggest that periodontal diseases may be linked with systemic diseases and conditions including cardiovascular diseases, diabetes, respiratory diseases, adverse pregnancy outcomes, and osteoporosis. Better understanding of this correlation will help both dental and medical professionals to determine the best approach to patient care. This review will focus on the current knowledge linking periodontal infections to a set of systemic diseases. While a number of interactions have been identified, additional research will be required to determine whether these associations are causal or coincidental, and to evaluate disease pathogenesis and potential therapeutic interventions. These findings place oral health in the perspective of systemic health, and they suggest that the dental and medical professions should develop even closer ties in the future.