Pleural empyema is a purulent pleural effusion. It is a known, albeit infrequent, complication of pneumonia. To treat a pleural empyema, antibiotics and sufficient drainage are required. Surgical intervention is often necessary and in some cases will include decortication. Decortication is the surgical removal of the organized material and pleural peel that forms in the later stages of pleural empyema. The Health Sciences Centre, Winnipeg, Manitoba, is the provincial referral centre for thoracic surgery. Since 2007, there has been a progressive increase in the number of decortications performed annually for pleural empyema with 5 performed in 2007 rising to 44 in 2013. An explanation for this approximately eightfold increase is not available. To investigate the observed increase in the number of decortications, this study will review the medical records of the 185 patients who underwent decortication since 2007. The following data will be analyzed: patient demographics, medical comorbidities, and the microbiology of the pneumonia and empyema. In addition, associated issues such as the anesthetic techniques used (single lumen versus double lumen tubes, use of regional anesthesia), surgical approaches (open versus thoracoscopic), peri-operative complications and hospital and intensive care unit length of stay will be described. The major complications to be analysed as outcomes are: 1) in-hospital mortality, 2) requirement for post-operative ventilation > 12 hours, 3) myocardial infarction, 4) acute kidney injury, 5) bleeding requiring transfusion > 2 units and 6) stroke. Univariate and multivariate regression analysis will be done to investigate the relationship between preoperative and intraoperative factors and the composite outcome of any major complication.