Abstract: Regenerated cellulose membranes with mean pore diameter 2r_f from 30 to 1000Å wereprepared from cellulose cuoxam solution in company with a microphase separation and after-treatment techniques.The r_f values of the membranes were measured by flow rate me-thod and the rejection Re on the membranes was measured on standard polystyrene samplesin toluene.The value of 2r_f was found in relatian with molecular weight M_w and rootmean square end distance < H² > ^1/2 of the rejected polystyrene in following equations:lg 2r_f = lg0.155 + 0.59 lgM_w and lg2r_f = lg 0.589 + 0.96 lg < h² > ^1/2.

Key words: regenerated cellulose membrane, pore diameter, rejection, polystyrene