A study of the high-frequency viscosity eta(infinity)' and of the high-frequency shear modulus G(infinity)' of a sterically stabilized latex is presented. The experimental measurements have been done using a torsional resonator described recently (J. Bergenholtz et al., J. Colloid Interface Sci. 202, 430 (1998)). The data of eta(infinity)' compare favorably with recent theoretical predictions and point to a partial draining of the steric layer by the solvent as expected, The high-shear modulus, however, is much lower than predicted by theory, The pair potential calculated from G(infinity)' by neglect of hydrodynamic interaction has a considerably longer range than expected from the structure of the steric layer. This points to the fact that hydrodynamic interactions are not negligible for these systems and must be included in a quantitative analysis of the high-frequency shear modulus G(infinity)'.