Polymer membrane filters are extensively used for sampling and collecting aerosols. This work explores the aerosol penetration of the polysulfone (PSF) membrane filters using monodisperse liquid aerosols. Three concentration-casting polysulfone solutions (15, 20 and 25%) were utilized to yield PSF membrane filters with variously sized pores. Additionally, the effects of various factors, including the species of the aerosol (dioctyl phthalate and potassium chloride), the size of the aerosol (0.03-0.5 mu m), the face velocity (5, 10 and 20 cm/s) and the relative humidity (30, 50 and 70%), on the aerosol penetrations, were estimated. Experimental results indicate that the penetrations of DOP liquid aerosols through 15, 20 and 25% PSF membrane filters with "Boltzmann charge equilibrium" are 3.1-9.1, 1.5-3.7 and 0.6-1.4%, respectively. The most penetrating size of the PSF membrane filters was around 0.05 mu m. Our results further demonstrate that penetration through PSF membrane filters fell as the concentration-casting solution increased, because the pore size of the PSF membrane filters declines as the concentration of the casting solution rises. Moreover, the penetration of solid aerosols through PSF membrane filters exceeds that of liquid aerosols, Penetration through the PSF membrane filters increases obviously with the flow rate when aerosol smaller than 0.21 mu m. When aerosol larger than 0.3 mu m, the variations of penetration through the PSF membrane filters become smaller at different flow rates. The relative humidity does not influence the performance of the PSF membrane filters. Results of this study demonstrate that the 25% PSF membrane filter has a larger q(F) than the 15 and 20% PSF membrane filters. (C) 2006 Elsevier B.V. All rights reserved.