Damage zone development in a triaxial stress state in poly(vinyl chloride) (PVC) and blends of PVC with methyl methacrylate-butadiene-styrene (MBS) core-shell rubber was analyzed as a function of temperature. The sequence of failure events at the notch root, core yielding and stress whitening, was shown to depend on the competition between the shear yield stress and the cavitation stress. The onset of cavitation was described by a critical mean stress and a critical volume strain. At low temperatures, a crescent-shaped stress-whitened zone formed at the notch root, and the critical mean stress was obtained by an elastic analysis. At temperatures in the ambient range and higher, shear yielding preceded cavitation at the notch root, and the critical mean stress was obtained by a plastic analysis. The transition from cavitation to shear yielding at the notch root coincided with a transition in the temperature dependence of the critical mean stress. Above the transition, the critical mean stress was much less sensitive to temperature than below the transition. Although this transition temperature was higher by about 30 degrees C in blends of PVC with 10 phr CPE (chlorinated polyethylene) rubber, the temperature dependence of the critical mean stress in both blends was similar.