Purification of phosphoric acid by reverse osmosis (RO) and nanofiltration (NF) was studied using different commercial membranes of common industrial use. Both techniques represent an interesting alternative in purifying industrial phosphoric acid solutions. RO is a good choice to purify solutions up to a concentration of 2 M. Among the RO membranes, SX01 (Osmonics) yields the best global performance: permeate flux of 13.5 L/m(2)h, at 1800 psi, 46.3% of acid permeation and 99.3% of global rejection of cationic impurities. The performance of membrane was better by applying a simple pretreatment with a solution of phosphoric acid/ethanol/water. However, NF is a better alternative since it can yield good results at concentrations up to 8 M. The DS5DL (Osmonics) is the NF membrane with the best global performance: permeate flux of 3.02 L/m(2)h at 1000 psi, 94.2% of acid permeation and 99.2% of cationic impurities rejection.