This paper presents the results of the first three stages of the surveillance specimen programs (one, two, and three years of irradiation) for the reactor pressure vessels (RPV) of W-213 type operated in Units 3 and 4 of nuclear power plant (NPP) Jaslovské Bohunice (EBO 3, EBO 4). The results of the tension and Charpy test specimens in both power reactors are analyzed. The changes of the mechanical parameters after irradiation are compared with the unirradiated condition of 15Ch2MFA steel for three material types: base material (BM), heat affected zone (HAZ), and weld metal (WM). Trends are presented for the shift of the transition temperature of both RPVs through end of operation. Some results from other WWER-440 units and aspects of the surveillance specimen program philosophy used in the WWER-440 reactor type are also presented. The data obtained from this program are used for the development of a database on irradiation degradation of all W-213 reactor vessels operated in the Czech and Slovak Federative Republic.