Double-layered polysulfone (PSF) membranes, containing cerium activated yttrium silicate (CAYS) as a fluor, were prepared from double casting of two polymeric solutions, and their morphology and radioactive capacity were compared with those of single-layered membranes. The backing, the bottom layer of double-layered membranes, was made of a binary casting solution of polysulfone and methylene chloride (MC), its cast film being solidified by vacuum evaporation. The second casting solution with dimethylformamide (DMF) as solvent was cast over the solidified backing film and coagulated by being immersed into a nonsolvent bath of water or methanol. The prepared membranes revealed two distinct, but tightly attached, double layers, their attachment being identified by the morphology of the interface between the two layers. Membranes prepared with CAYS in the casting solution have more developed macropores than those prepared without CAYS. In the radionuclide detection test of the CAYS-impregnated membranes, the membranes solidified by water precipitation showed better detection efficiency than those solidified by methanol precipitation. Its superior efficiency is not due to better holding of the radioisotopes, but due to greater density of CAYS in the membrane surface region. In the comparison with single-layered membranes, the double-layered membranes showed a greater ability in holding the radionuclides, spotted on the surface, as well as an improvement in physical strength because of the dense backing layer. (C) 2003 Elsevier B.V. All rights reserved.