Transport measurements of selected fluids through porous membranes provide information on precise statistical moments of the membrane pore-size distribution (PSD). It is assumed that membrane porosity, ~T,is distributed on different pores sizes which are statistically distributed. Mean pore sizes are determined on the basis of statistical moment analysis. This paper focuses in the special case of determining PSD in microfiltration (MF) membranes from a collectíon of experíments that include porosity and bubble point determinations and liquid and gas permeations.