The effectiveness of vaccination against red sea bream iridoviral disease (RSIVD) was evaluated using two kinds of vaccines in red sea bream (Pagrus major). For one vaccine, RSIV-infected GF cells were inactivated with formalin (1.0% v/v) for 10 days at 4°C and for the other the cell culture supernatant of RSIV-infected GF cells was inactivated with formalin (0.3% v/v) for 10 days at 4°C. Juvenile red sea bream were intraperitoneally injected with vaccines and after 10 days the fish were RSIV-challenged by intraperitoneal injection. Statistical analysis showed significantly high survival rates in the vaccinated groups than that of the respective control groups, indicating the protection is induced by the vaccination.In addition, the expression of the virus specific antigens in the spleen was examined for vaccinated and control fish after RSIV challenge by immunofluorescence test. The result that the expression of antigens was weaker in the vaccinated fish compared with the control fish supported the efficacy of the vaccination.