The mass of gamma-globulin deposited onto an Anodisc(R) alumina membrane with a nominal pore diameter of 0.1 mum has been measured at several concentrations and pH. This deposition resulted from filtering through the membrane in a continuous recirculation device. The low concentration deposition can be assigned mainly to adsorption, that can be studied as a function of the electrostatic forces between the solute and the membrane. A sharp maximum in the adsorbed mass for zero electrostatic force was obtained. At high concentrations, accumulation (non-adsorptive deposition) has also to be taken into account at alkaline pH as confirmed by flux decay experiments and retention measurements. The irreversible deposition (understanding irreversible as referring to deposition that do not disappear when the flux through the membrane stops) has been studied by imaging the surface of the membrane after filtration using atomic force microscopy (AFM). These images give insights into how and where adsorption takes place.