The literature on filtration theory and past experimental work was reviewed and critiqued with regard to the needs of the EPA relative to stationary source sampling. A laboratory evaluation of aerosol collection efficiency and flow resistance of filters potentially useful in EPA sampling programs was designed with respect to several variables, including particle size (0.05, about 0.1 and 0.5 micrometers MMD); gas velocity (4, 12, 30, 83 and 126 cm/sec); and aerosol composition and density (g/sq cm)-DOP(1.0), Na Cl (2.17),Be SO4 . 2 H2O(2.36), Pb (NO3)2 (4.53), and Cd I (5.67). Filter collection efficiencies were measured for the various evaluation parameters with a DOP penetrometer or sodium flame photometer. With two exceptions, collection efficiencies of greater than 99 percent were obtained for all filters and test conditions. The exceptions, tested with 0.3 micrometers MMD Na Cl aerosol, were Millipore Mitex and Whatman 41 filters, with collection efficiencies of 75 and 50 percent, respectively. The other membrane filters (Millipore AA and Fluoropore) exhibited high flow resistance at 30 and 83 cm/sec and could not be tested at higher flow rates.