The detoxification capacities of single-pass albumin dialysis (SPAD), the molecular adsorbents recirculation system, (MARS) and continuous veno-venous hemodiafiltration (CVVHDF) were comparedin vitro. In each experiment 4,100 mL of toxin-loaded human plasma was processed for 6.5 hours. MARS treatment (n = 6) was undertaken in combination with CVVHDF. For SPAD (n = 6) and CVVHDF (n = 6) a high-flux hollow fiber hemodiafilter (identical to the MARS filter) was used. Levels of ammonia, urea, creatinine, bilirubin, and bile acids were determined. Concentrations before and after application of detoxification procedures were expressed as differences and were compared using the Kruskal-Wallis test.Post hoc comparisons for pairs of groups were adjusted according to Bonferroni-Holm. Time, group, and interaction effects were tested using the nonparametric ANOVA model for repeated measurements. SPAD and CVVHDF induced a significantly greater reduction of ammonia levels than MARS. No significant differences were found among SPAD, MARS, and CVVHDF with respect to other water-soluble substances. SPAD induced a significantly greater reduction in bilirubin levels than MARS. Reductions in bile acid levels were similar for SPAD and MARS. When operating MARS in continuous veno-venous hemodialysis mode, as recommended by the manufacturer, no significant differences in the removal of bilirubin, bile acids, urea, and creatinine were found. However, MARS in continuous veno-venous hemodialysis mode was significantly less efficient in removing ammonia than MARS in CVVHDF mode. In conclusion, the detoxification capacity of SPAD is similar to or even greater than that of MARS. (Hepatology 2004;39:1408-1414.)