Propofol and midazolam are widely used for intravenous sedation in critically ill patients. Their immunomodulatory effects may become more prominent when used for prolonged periods in Intensive Care Unit (ICU) patients with compromised immune functions as a result of infection, trauma, cancer or immune deficiency syndromes. The aim of this study was to investigate the production of cytokines and acute phase response in surgical intensive care unit (ICU) patients as a reflection of their immune response to prolonged administration of propofol and midazolam.