The adsorption kinetic at the air-aqueous phase interface of bovine serum albumin (BSA) has been studied. Data are presented and analyzed for short adsorption time taking into account the diffusion of the protein from the bulk phase to the interface, in the absence of convection. The adsorption kinetics was determined by surface tension measurements as a function of time, protein concentration in the bulk phase, and bulk phase composition (aqueous solutions of ethanol and sucrose). The temperature (20 degreesC), the pH (7.0), and the ionic strength (0.05 M) were maintained constant. The adsorption kinetics at short adsorption time, since the surface pressure is lower than 5 mN/m, is diffusion controlled. The diffusion of BSA to the interface increases with the protein concentration in the bulk phase and in aqueous sucrose solutions, but it decreases in ethanol aqueous solutions.