We report on the preparation and characterization of mesoporous silica membranes via nucellar templating using the non-ionic ethylene oxide-propylene oxide-ethylene oxide tri-block copolymer surfactant. Pluronic P123, as a template under various template/silica volume percentages (V-TS%). The silica membranes were prepared by dip coating silica sols onto porous alpha-alumina Supports followed by calcination to remove the template. The membranes were characterized by single gas permeation and permporometry measurements. Using a V-TS% of 33 we found that silica membranes comprised of three dip/fire cycles resulted in highly reproducible continuous membranes with minimal defects. Helium and nitrogen permeance values were of the order of 10(-6) mol m(-2) s(-1) Pa-1. The pore size distribution, determined from permporometry measurements, indicated a dominant peak at 5 nm diameter and approximately 10% microporosity. In addition, there was 8-10% permeance through pores with diameters between 15 and 40 nm. At higher VTS% (47.5 and 65) the silica membranes had considerable bypass flow. The pore size distribution (PSD) of the membrane via permporometry indicated a shift to smaller values for the membrane when compared to the PSD of the powder from the calcined dipping sol, determined by nitrocen adsorption/desorption. (c) 2006 Elsevier B.V. All rights reserved.