This article provides a brief review of findings from epidemiological studies of periodontal disease that have been generated over the past five years. In line with the conclusions of the 1996 World Workshop in Periodontics, the recent data support the concept that early onset periodontitis appears to be rather infrequent, while advanced adult periodontitis, leading to severe loss of supporting periodontal tissues and tooth loss, does not exceed a prevalence of 10-15% in most populations. However, a number of important issues remain unresolved. It is still not clear whether the prevalence of these diseases has shown an overall decline in recent years. In fact, retention of teeth in older age may contribute to an increase. Analytical epidemiological studies have been increasingly successful in identifying a handful of risk factors for disease onset and progression. These include colonisation at high levels by certain subgingival bacteria, environmental exposures such as cigarette smoking, and systemic conditions such as diabetes mellitus. Importantly, the molecular basis of host susceptibility has recently begun to be unraveled. Research efforts are now focused on creating multi-factorial models to assess the risk for disease, prior to the development of irreversible damage. Importantly, the role of periodontal infections as a modifier of systemic health is being increasingly explored.