The viscoelastic properties of dispersions of uniform glass spheres (diameter approximate to 10 mu m) in poly(dimethylsiloxane) (PDMS) were studied to evaluate the possibility of hydrodynamic slip at boundaries between the spheres and the PDMS matrix. The particle-matrix interfacial interactions are controlled by introducing a fluoro silane coating to the glass beads that reduces the surface energy of bare glass from over 200 mJ/m(2) to a level of ca. 20 mj/m(2). It is shown that the filler (i.e., glass beads) contribution to the overall suspension viscosity decreases significantly when the surface energy of treated beads approaches that of the PDMS matrix. From the point of view of stress transfer and theology, we report the first set of theological data supporting the concept of ideal slip. Our results also provide evidence for stress-induced interfacial slip. At high stress the difference in viscosity between a suspension of nontreated glass spheres and that of silane-treated spheres is larger than it is at low stress. Currently we do not know whether the stress-induced slip is due to debonding of interfacial chains off the glass beads or disentanglement of these chains with the matrix chains or a combination of both.