Objectives: The aim of this study was to investigate the dialysis adequacy of low-flux versus high-flux membranes in Hemodialysis Patients. Patients and Methods: Forty hemodialysis patients participated in this cross-over clinical trial. Two sessions of lux and lux membrane dialysis were performed in the first and second stage of the trial. In both stages blood samples before and dialysis were taken and sent to laboratory for assessment. Blood urea nitrogen (BUN), KT/V (K = dialyzer clearance of urea, t = dialysis time, V = volume of distribution of urea) and the urea reduction ratio (URR) indexes used to determine dialysis adequacy. Data were analyzed by using SPSS16 and test and pair test. Results: The mean of KT/V was 1.27 ± 0.28 in lux and 1.10 ± 0.32 in membrane which, differences statistically significant ( P = 0.017). The mean of URR was 0.65 ± 0.09 in and 0.61 ± 0.14 in lux membrane which differences not statistically significant ( P = 0.221). Conclusions: The High-Flux membrane had better dialysis adequacy, so we suggest the use of High-Flux membrane in Hemodialysis centers.