The nonisothermal dynamics of the unstable crack growth in polymers is investigated. The system of general equations (the heat conductivity equation and the crack propagation equation) is formulated taking into account the near-crack-tip plasticity, the specific geometry of the specimen (Chevron) and real temperature dependences of the material parameters (flow stress, critical stress intensity factor, specific heat, etc.). Num­erical analysis of general equations reveals the existence of the high-frequency oscillations of the crack velo­city and the crack-tip temperature in the course of the crack propagation. The stage of the oscillational crack advance is completed by the arrest. The conditions of crack arrest are discussed.