Inadequacy of dialysis is one of the main causes of death in hemodialysis patients. Some studies have suggested that high-flux membrane improves the removal of moderate-sized molecules while other studies indicate no significant effect on them.This study aimed to investigate the dialysis efficacy of low-flux versus high-flux membranes in hemodialysis patients.Forty hemodialysis patients participated in this cross-over clinical trial. Two sessions of low-flux and high-flux membrane dialysis were performed consecutively, in the first and second stage of the trial. In both stages, blood samples before and after the dialysis were taken and sent to the laboratory for assessment. Blood urea nitrogen (BUN), KT/V and the urea reduction ratio (URR) indexes were used to determine dialysis efficacy. Data were analyzed using t test and paired t test.The mean KT/V was 1.27 ± 0.28 in high-flux and 1.10 ± 0.32 in low-flux membrane which, these differences were statistically significant (P = 0.017). The mean of URR was 0.65 ± 0.09 in high-flux and 0.61 ± 0.14 in low-flux membrane, which these differences were not statistically significant (P = 0.221).The high-flux membrane had better dialysis adequacy, so we suggest using high-flux membrane in hemodialysis centers.