['To evaluate the prognostic implication of changes in postoperative B-type natriuretic peptide (BNP) concentrations in patients undergoing cardiopulmonary bypass for cardiac surgery.', 'A retrospective analysis of prospectively collected clinical data.', 'Cardiothoracic surgery and an intensive care unit (ICU) in a university hospital.', 'The present study included a total of 407 consecutive patients undergoing cardiac surgery.', 'None.', 'BNP concentrations were measured on admittance to the ICU (D0) and at day 1 after surgery. Patients were divided into quintiles according to their BNP level on admittance to the ICU. The predictive value of absolute changes in BNP levels during the first 24 hours postoperatively was analyzed with Kaplan-Meier estimates of survival and Cox multivariate proportional analysis. Prognostic factors for impaired midterm survival included elevation of the BNP level (HR, 7.3/ log10(x); 95% confidence interval, 1.8-29, p = 0.005). The BNP levels of patients undergoing isolated valve surgery or valve and concomitant CABG surgery were significantly higher (p = 0.012 and p = 0.032, respectively) than those undergoing isolated coronary artery bypass graft surgery. Patients in higher quintiles required ventilation for a longer time (p < 0.001), and prolonged inotropic support (p < 0.001). The mean plasma BNP concentration of 172 pg/mL (median, 64; interquartile range, 172) on arrival at the ICU had a sensitivity of 75% and a specificity of 74% for predicting 1-year mortality.'] Does postoperative increase in B-type natriuretic peptide levels predict adverse outcome after cardiac surgery?