The cytokines play a main role as mediators in immunological response. IL-6 with IL-2 and INF-gamma take a part in stimulation and differentiation of cytotoxic lymphocytes T, in stimulation and production of antibodies by lymphocytes B, in stimulation of production of acute phase proteins by hepatocytes and in proliferation of mezenchymal cells. The aim of this study was a comparison of concentrations of IL-6 and sIL-6R in children with chronic renal failure on dialysis treatment (11 children), continuous ambulatory peritoneal dialysis (10 children) and conservative therapy (18 children). They concluded that the concentration of IL-6 in children on hemodialysis therapy comparing with children on conservative therapy was nearly significant.