Abstract Adsorption of bovine serum albumin (BSA) on to large-size monodisperse latices was investigated. Polystyrene (PS) latices in two different sizes with hydroxyl, amino and carboxyl groups on their surfaces were produced by following a two-step polymerization procedure. The effects of pH and ionic strength of the medium on BSA adsorption capacity of the latices were investigated in the existence of two different anions and three different cations, Cl − and SCN − and Na + Call and Mg 2+ respectively. Maximum adsorption capacities for all latices were obtained near the isoelectric point of BSA. No BSA adsorption was observed with PS latex, especially in the alkaline pH region. The BSA adsorption capacity decreased with increasing ionic strength. Different adsorption behaviors were noted in the PS latices having functional groups on their surfaces.