Both receding and advancing contact angles of pure water and BSA solutions against the active layers of several retentive ultrafiltration membranes are studied here. In particular, three membranes from desalination systems, whose active layers are made of aromatic polyamides: G5, G20 and G50 have been chosen. It has been shown that these membranes are hydrophilic with equal advancing contact angles against pure water while the receding ones decrease with increasing pore radii. Finally, both the contact angles against the BSA solutions are studied at different pH and concentrations. It is shown that the stationary advancing contact angles correspond to the early adsorption steps while receding ones correspond to the final adsorption level. When analyzed within this frame, the results obtained can easily be explained in terms of the qualitatively known molecule-molecule and molecule-membrane surface interactions. (C) 1999 Elsevier Science B.V. All rights reserved.