The aim of the study was to evaluate the influence of follow fiber dialyzers reprocessing procedure on urea kinetic modeling parameters, dialysis effectiveness for small molecules and effective clearance/predicted clearance ratio. Fifty patients (27 F, 23 M) aged 18-61 years (mean 47) being on maintenance hemodialysis due to end stage renal failure for 4-136 months were included into the study. Patients were treated 3 times a week with blood flow 160-290 ml/min and dialysate flow 500 ml/min. The dialysis time was calculated individually based on urea kinetic modeling parameters. Reprocessing of dialyzers was performed using Renatron RS 8300 and Renalin as sterilized agent. Dialysers with ppr below 80% were excluded from the use. Mean values of dialysis index Kt/V, TAC and dialysis effectiveness (Ct/C0) for urea, creatinine, uric acid and kalium as well as values of effective/predicted clearance ratio for consecutive reprocessing procedures were compared with the results obtained for the new dialyzers. There was no significant influence of reprocessing procedure on Kt/V, TAC and Ct/C0 for tested substances and studied clearances. The obtained results indicates that dialysers reprocessing procedure performed according to the described protocol was safe and didn't decrease dialysis effectiveness.