The main results of a complex investigation carried out in Russia of post irradiation annealing and reembrittlement of WWER-440 reactor pressure vessel materials are presented. The dependence of the Charpy transition temperature recovery on annealing temperature and fluence was established. Charpy specimens were reirradiated after annealing at 340, 380, 420, and 460°C. Experimental values of the Charpy transition temperature after reirradiation are compared to that predicted by three methods. At annealing temperatures equal to or above 420°C, results of the analysis indicate that, of the methods investigated, the “lateral shift” method gives the best result for estimating the transition temperature shift due to reirradiation.