A quantitative model for cavitation and consequent dilatational yielding in multiphase plastics (1, 2) is reviewed and new developments are reported and compared with experimental results. According to the model, cavitation can occur by debonding at phase boundaries or by nucleation of voids within a soft polymeric phase when the stored volumetric strain energy density within the rubber phase exceeds a critical value. The model relates the critical volume strain required for cavitation to the properties of the particle: its size, shear modulus, surface energy and failure strain in biaxial extension. Subsequent to cavitation of the rubber particles, the yield behavior of the polymer is significantly altered, especially at high triaxiality, and can be modeled by the modified Gurson equation proposed by Lazzeri and Bucknall (1, 2). Particle cavitation also increases the rate of yielding. On increasing the strain level in the material, the deformation will tend to assume an inhomogeneous character leading