We measured the degree of immunity of 326 Korean children to rubella virus by enzyme-linked immunosorbent assy (ELISA). They were admitted to Pediatrics Unit of Yonsei Medical Center between April and July, 1980 with various illnesses excluding rubella disease. Among the 326 tested, 172 cases gave a positive titer of antibodies (mainly, IgG and IgM antibodies) and 127 had IgG antibody against rubella virus antigen. These represented 52.8% and 39.0%, respectively, of the total number of children tested. There was no significant difference in the rate of positivity between sex, but the positive rate increased as the age increased. The antobody titers of positive individuals to rubella virus were higher among the older children. Results and a brief outline of the ELISA method for serodiagnosis of rubella in clinical use will be discussed.