Modified ultrafiltration (MUF) is a technique able to remove the excess body fluid and inflammatory mediators associated with the use of a cardiopulmonary bypass (CPB). It has been shown to reduce morbidity after cardiac operations in children. Application of MUF after adult cardiac operations has also been suggested being associated with a lower prevalence of early morbidity. However, the relationship between the concentration of mediators in the blood and postoperative morbidity remains yet to be proved. In this study, changes of various chemical mediators in the filtrate and blood before and after MUF have been evaluated in adult patients. Significant reductions of blood levels of inflammatory cytokines were not observed after MUF. On the other hand, MUF significantly elevated hematocrit, number of red cells, concentrations of albumine, coagulation Factor VII and X, platelet factor (PF)-4, and antithrombin (AT-) III.