The adsorption of phenol on inorganic carbon-supported microfiltration and ultrafiltration membranes has been determined. Using the statistical Student＇s t-test, it has been shown that phenol adsorption data are well fitted to the Langmuir and BET isotherm equations. It was thus concluded that the adsorption of phenol was monomolecular and that the specific surface area (SSA) calculated from these data was essential. M1 and M2 ultrafiltration membranes were found to have a higher SSA than microfiltration M14 and carbon support membranes. Assuming that a simple model of the porous structure consisted of a packed bed of spherical particles, it was possible to determine an apparent average pore diameter from SSA data using the Carman-Kozeny equation. The SSA determined from phenol adsorption was found to be close to that measured from mercury porosimetry for the microfiltration membrane and carbon support. Such a result is due to the fact that there is a common basis between the Carman-Kozeny equation employed in the adsorption method and the determination of the ratio 4V/A (V = total porous volume, A = total pore area) in the mercury porosimetry method (as both methods consider a constant volume/surface ratio of the pores along the microporous membrane thickness).