['Experimental models show that apolipoprotein CI (apoCI) binds and enhances the inflammatory response to endotoxin. We studied in patients undergoing cardiopulmonary bypass surgery (CPB) and experiencing endotoxemia during reperfusion whether plasma apoCI levels correlate with the inflammatory response and perioperative cytokine release.', 'Prospective, observational, clinical cohort study.', 'Operating room (OR) and intensive care unit (ICU) of a university hospital.', 'One hundred fifty-nine consecutive patients > 18 years of age (66% males =105), median age 65 and 67 years for males and females, respectively) undergoing elective cardiothoracic surgery with cardiopulmonary bypass.', 'None.', 'Baseline apoCI, apoCIII, total cholesterol and triglyceride levels, and perioperative endotoxin and TNF-alpha levels were determined.', 'High preoperative plasma apoCI, but not apoCIII, levels were associated (p < 0.05) with increased perioperative levels of TNF-alpha in patients experiencing endotoxemia. This association was not observed in patients without endotoxemia.'] Do preoperative apolipoprotein CI levels correlate positively with the proinflammatory response in patients experiencing endotoxemia following elective cardiac surgery?