A model for dilatational yielding in rubber-toughened polymers, which was proposed in an earlier paper, is developed further. According to the model, deformation begins with cavitation of the rubber particles, and progresses through the growth of dilatational bands, which are cavitated planar yield zones combining inplane shear with extension normal to the band. The model is used to predict band angles and other characteristics of yielding in toughened plastics, including the conditions under which polymers yield without cavitating. Electron micrograph evidence for the formation of dilatation bands is presented, and the influence of these bands on deformation and fracture behaviour is discussed, using a novel method of presentation based on cavitation diagrams.