In this paper, the plane-strain finite deformations near the tip of a blunted crack between a viscoplastic glassy polymer and a rigid substrate are investigated assuming small-scale yielding. A constitutive model accounting for the intrinsic softening upon yield and the subsequent orientational strain hardening is adopted to simulate the typical behavior of glassy polymers. The influence of mode mixity and plasticity characteristics on the near-tip fields is studied. The distribution of interface normal stress, as the cause of interface delamination, is analyzed. Based on these results, a simple delamination criterion involving an interface bond strength is adopted to estimate the interface toughness. The interface bond strength governs the extent of plastic deformation that can accumulate prior to interface delamination, and the contribution of plastic dissipation to the interface toughness depends on the mode mixity and the plasticity characteristics. (C) 2004 Elsevier SAS. All rights reserved.