Background: Hemodiafiltration (HDF) is a form of renal replacement therapy. Tumor necrosis factor (TNF) is proinflammatory cytokine and has been reported to be elevated in adults with ESRD on hemodialysis. Objective: To compare TNF levels and dialytic change between conventional hemodialysis and on-line hemodiafiltration. Methods The study included 2 groups of pediatric patients (<15 years of age) with ESRD; group I (n=16) treated with on-line HDF and group II (n=20) with conventional low-flux hemodialysis. Plasma TNF was measured for all patients at the beginning and termination of a dialysis session. Results: TNF levels in patients treated with online HDF (106.2 +/- 57.5 pg/mL) were lower than in those on conventional HD (180.5 +/- 71.7 pg/mL); p=0.002. Both groups had significantly higher levels than controls. Post-dialysis values were 82.1 +/- 36.1 pg/mL and 179.1 +/- 83.5 for HDF and HD respectively, both reflecting insignificant reductions (p=0.17 and 0.98). Conclusion: In children with ESRD, online HDF is associated with lower plasma concentrations of proinflammatory cytokines (as TNF) than conventional HD.