The surface shear properties of protein adsorption layers at the air/water interface have been studied at small periodic deformations by means of a modified torsion pendulum instrument. Surface shear rheological investigations of different proteins and protein/surfactant mixtures are discussed. As proteins, human albumins and gelatin are used without and in the presence of the anionic surfactant sodium dodecyl sulphate. The results are discussed in terms of adsorption layer structure and the interaction between protein molecules and of proteins with surfactants.