AIM: To evaluate whether treatment with the Prometheus(R) system significantly affects cytokines,coagulation factors and other plasma proteins.METHODS: We studied nine patients with acute-onchronic liver failure and accompanying renal failure.Prometheus(R) therapy was performed on 2 consecutive days for up to 6 h in all patients. Several biochemical parameters and blood counts were assessed at regular time points during Prometheus(R) treatment.RESULTS: We observed a significant decrease of both protein-bound (e.g. Bile acids) and water-soluble (e.g.ammonia) substances after Prometheus(R) therapy. Even though leukocytes increased during treatment (P＜ 0.01),we found no significant changes of C-reactive protein,interleukin-6, and tumor necrosis factor-α plasma levels (all P ＞ 0.5). Further, antithrombin 3, factor Ⅱ and factor V plasma levels did not decrease during Prometheus(R)therapy (all P ＞0.5), and the INR remained unchanged (P =0.4). Plasma levels of total protein, albumin, and fibrinogen were also not altered during Prometheus(R)treatment (all P ＞ 0.5). Finally, platelet count did not change significantly during therapy (P= 0.6).CONCLUSION: Despite significant removal of proteinbound and water-soluble substances, Prometheus(R)therapy did not affect the level of cytokines, coagulation factors or other plasma proteins. Thus, the filters and adsorbers used in the system are highly effective and specific for water-soluble substances and toxins bound to the albumin fraction.