Asymmetric membranes for ultrafiltration were obtained from PVDF/PMMA blends. Addition of 1% PMMA to the casting solution increases the water permeability 14-fold without loss of retention. Pore size distribution, evaluated by a modified bubble point test, showed a large increase in number of pores with size between 10 and 30 nm. The addition of PMMA also increases the size of finger-like cavities as shown by scanning electron microscopy.7312535