Track-etched polycarbonate (PC) microfilters were successfully prepared by tracking with fission fragments in the Thai Research Reactor-1/Modification-1 nuclear reactor and chemical etching with sodium hydroxide aqueous solutions. The porosity of the as-prepared microfilters can be controlled by varying the exposure time in the nuclear reactor and the average pore diameter by varying the etching conditions. In the present work, the average pore diameter of the as-prepared microfilters ranged from similar to 2.0 to 9.5 mu m (workable values) and the highest pore density achieved was similar to 150,000 pores cm(-2). It was found that chemical etching also caused a reduction in the film thickness. Fourier-transform infrared spectroscopy results suggested some modifications in the chemical structure of the PC molecules after both nuclear tracking and chemical etching steps. Lastly, water permeability of the as-prepared, track-etched PC microfilters was found to increase with increasing average pore diameter. (c) 2006 Wiley Periodicals, Inc.