Permporometry as well as nitrogen adsorption-desorption techniques have been applied to study the pore size distribution in γ-alumina membranes with a pore radius ranging from about 2 nm to 10 nm. The permporometry technique measures the active pores only, while nitrogen adsorption-desorption measures the active as well as the passive pores. The pore size distribution in the porous ceramic membrane supported with an -alumina substrate (supported membrane) was determined by using permporometry, while the membrane without a supporting substrate (unsupported membrane) was characterized by nitrogen adsorption-desorption. The experimental results of permporometry and nitrogen adsorption-desorption indicate that the size distribution of the active pores in the supported membranes is similar to that of the active and passive pores in the unsupported membranes. The -alumina supporting substrate seems to have no detectable influence on the size distribution of the active pores of the ceramic membranes studied.