- A phenomenological framework for describing the process of interfacial decohesion from initial debonding through complete separation is described. Within this framework constitutive relations are specified independently for material phases and for the interface. The interface is characterized by a traction-displacement relation so that dimensional considerations introduce a characteristic length. Also, interfacial decohesion can be predicted without the introduction of an additional failure criterion. Issues related to the characterization of interface response, to the nucleation and propagation of crack-like defects and to void nucleation are discussed. 1992.