The dynamic surface elasticity of solutions of β-casein/surfactant mixtures was measured as a function of surface age and surfactant concentration. Small additions of ionic surfactants changed strongly the kinetic dependence of the dynamic surface elasticity of protein solutions. The shape of the kinetic curve depended on the charge of the surfactant ion. The results can be explained by strong electrostatic interactions between charged amino acid residues in the protein and surfactant ions, and different distributions of positive and negative charges along the protein chain. It is shown that small additions of ionic surfactants can probe the mechanism of protein adsorption. The obtained results confirm the consecutive transitions of the relatively hydrophilic and hydrophobic parts of a β-casein molecule into the subphase as loops and tails. Unlike the case of β-casein/ionic surfactant solutions, the effect of small additions of a nonionic surfactant with high surface activity can be described as a gradual displacement of /5-casein from the adsorption layer.