We studied polymer-polymer interfacial slip in bilayer films of highly immiscible (interaction parameter, chi congruent to 0.1) polyethylene and fluoropolymer from medium to higher shear stresses (10-200 kPa) using both visualization and stress reduction. We found good agreement between results from the two methods as well as with previous studies using multilayers by Lee et al. [J. Rheol. 53, 893-915 (2009)] and visualization of flow in a transparent capillary by Migler et al. [J. Rheol. 45, 565-581 (2001)]. We observed two power-law regions: V-slip proportional to tau(6.2) with a transition to V-slip proportional to tau(1.8) at 50 kPa. This is in contrast to the theory of Brochard-Wyart and de Gennes [C. R. Acad. Sci., Ser. II: Mec., Phys., Chim., Sci. Terre Univers 317, 13-17 (1993)], which predicts a transition from infinite slope to a slope of one at a critical stress. (C) 2010 The Society of Rheology. [DOI: 10.1122/1.3479389]