BACKGROUND:: No externally validated risk score for postoperative pulmonary complications (PPCs) is currently available. The authors tested the generalizability of the Assess Respiratory Risk in Surgical Patients in Catalonia risk score for PPCs in a large European cohort (Prospective Evaluation of a RIsk Score for postoperative pulmonary COmPlications in Europe). METHODS:: Sixty-three centers recruited 5,859 surgical patients receiving general, neuraxial, or plexus block anesthesia. The Assess Respiratory Risk in Surgical Patients in Catalonia factors (age, preoperative arterial oxygen saturation in air, acute respiratory infection during the previous month, preoperative anemia, upper abdominal or intrathoracic surgery, surgical duration, and emergency surgery) were recorded, along with PPC occurrence (respiratory infection or failure, bronchospasm, atelectasis, pleural effusion, pneumothorax, or aspiration pneumonitis). Discrimination, calibration, and diagnostic accuracy measures of the Assess Respiratory Risk in Surgical Patients in Catalonia score's performance were calculated for the Prospective Evaluation of a RIsk Score for postoperative pulmonary COmPlications in Europe cohort and three subsamples: Spain, Western Europe, and Eastern Europe. RESULTS:: The full Prospective Evaluation of a RIsk Score for postoperative pulmonary COmPlications in Europe data set included 5,099 patients; 725 PPCs were recorded for 404 patients (7.9%). The score's discrimination was good: c-statistic (95% CI), 0.80 (0.78 to 0.82). Predicted versus observed PPC rates for low, intermediate, and high risk were 0.87 and 3.39% (score <26), 7.82 and 12.98% (≥ 26 and <45), and 38.13 and 38.01% (≥ 45), respectively; the positive likelihood ratio for a score of 45 or greater was 7.12 (5.93 to 8.56). The score performed best in the Western Europe subsample - c-statistic, 0.87 (0.83 to 0.90) and positive likelihood ratio, 11.56 (8.63 to 15.47) - and worst in the Eastern Europe subsample. The predicted (5.5%) and observed (5.7%) PPC rates were most similar in the Spain subsample. CONCLUSIONS:: The Assess Respiratory Risk in Surgical Patients in Catalonia score predicts three levels of PPC risk in hospitals outside the development setting. Performance differs between geographic areas. Copyright © 2014, the American Society of Anesthesiologists, Inc.