Abstract The most important proteins in animal blood as haemoglobin, bovine serum albumin and -globuline were filtered in experimental UF membranes. The membranes were prepared in our laboratory by the traditional phase inversion process using as polymer a new polyamide. These membranes were characterized by measuring their initial water fluxes, and after that the protein solutions were ultrafiltered. The flux decline and membrane fouling were studied in order to obtain the best operating conditions for a future pilot plant scale application.