A proposed theoretical model describes colloids deposition on a membrane surface accounting for surface interactions. A mass-transfer equation links the deposition rate to hydrodynamic conditions (permeation and tangential flow through a boundary layer thickness, delta) and to physicochemical properties of the suspension (diffusion, D, and potential barrier between particles, V-B). This equation predicts the existence of a critical flux, J(crit) for ultrafiltration, reverse osmosis, or microfiltration of large-size colloids as : [GRAPHICS] Some of the trends observed when processing protein solutions are explained by this model. Previous experimental data for various colloids or our data with a clay suspension in the presence of electrolytes are also compared to predictions of our model. It explains the "flux anomaly" for particle sizes between 10 nm and 1 mu m.