Piperazine containing polymers, having no ＇H＇ atom at amide nitrogen have been prepared from diaminobenzanilides and diacid chlorides by low temperature polycondensation method. These polymers have been characterised by inherent viscosity, percent moisture regain, solubility, IR and thermal analysis. Amount of chlorine absorbed by the polyamides has been calculated by titrating polymer suspension with sodium thiosulphate. Membranes were cast from the polymer solution in dimethyl acetamide containing lithium chloride as an additive. These membranes were studied for reverse osmosis (RO) performance in salt water with and without chlorine containing medium.