In rotational oscillatory rheological measurement techniques involving the plate-plate and cone-plate geometries, the interface between the measured liquid and the ambient atmosphere is sheared to the same extent as the liquid sample. In this paper, we look at the influence of a rheologically distinct lateral surface on the measured properties of the liquid and surface system when the surface is dynamically coupled to the bulk fluid. Inertia is taken into account, thus allowing for nonquasi-static velocity profiles in the massless surface film itself (C) 2003 Elsevier Science (USA). All rights reserved.