BACKGROUND: Empyema is a suppurative infection of the pleural space. Without prompt treatment, it can result in significant hospital stays, more invasive treatments as it progresses, and substantial morbidity and mortality.OBJECTIVES: The primary objective of the present study was to evaluate whether there has been an increasing incidence of empyema in Canada. A secondary objective was to investigate whether this increase disproportionately affects any age group.METHODS: The Discharge Abstract Database of the Canadian Institute for Health Information was used to evaluate national empyema data.RESULTS: There were 11,294 patients identified with empyema over the nine-year period of the present study, of whom 31% were women. The mean (± SD) length of stay was stable throughout the study at 21.82±33.88 days, and 63.4% were discharged home. The incidence rate ratio (IRR) was defined as the ratio of the incidence rate of medical empyema in 2003 divided by the incidence rate in 1995. Medical empyema increased significantly (IRR 1.30, 95% CI 1.20 to 1.41; P<0.001), as did empyema of unknown cause (IRR 1.29, 95% CI 1.08 to 1.54; P=0.005), while surgical empyema did not appear to increase (IRR 1.17, 95% CI 0.97 to 1.43; P=0.114). A Poisson regression showed an increase in the indirect age-standardized IRR during the study period (IRR 1.025, 95% CI 1.018 to 1.032; P<0.001). The IRR for patients younger than 19 years of age from 1995 to 2003 was 2.20 (95% CI 1.56 to 3.10), while the IRR in patients older than 19 years was 1.23 (95% CI 1.14 to 1.34).CONCLUSIONS: The present study demonstrates the increasing rate of empyema in Canada and shows a change in pattern of disease. The disproportionate rate change in the pediatric population suggests a high-risk group that needs to be addressed. In the adult population, while cause is unknown, it is necessary to continually educate front-line physicians to confront both the increased burden of this disease, caused by an aging population, and the underlying increasing rate of empyema in Canada.