The use of membrane distillation in the concentration of protein solutions is proposed. Semidilute BSA solutions (concentrations ranging between 0.40 and 1.00%), at pH 7.4 were employed. Transmembrane volume fluxes and evolution of the BSA concentration were measured at different conditions. Temperatures ranged between 20 and 38 degrees C. The filtration cell was operated at laminar regime with tangential velocities of 5.9 and 8.9 cm.s(-1). Special attention was devoted to analysis of the temperature polarization and fouling effects. The results obtained show that fouling effects are practically absent in membrane distillation operations with BSA solutions, at least for concentrations up to 1.00% w/w and in the range of crossflow velocities employed. This may be due to the fact that the transmembrane fluxes are below the value of the critical flux for fouling.