PURPOSE: To evaluate the efficacy and need for boosting of mumps vaccine, we measured the degree of immunity of previously vaccinated healthy children with the age from 15 months to 15 years. METHODS: We measured mumps specific IgG & IgM antibody titers of 96 children, vaccinated at the age of 15 months, with the age from 15 months to 15 years by ELISA.(Enzyme linked immunosorbent assay) RESULTS: The results are as follows 1) Sixty three cases(65.6%) were positive for mumps IgG antibody and 18 cases (18.7%) were positive for IgM antibody. 2) Mumps IgG antibody decreased between the age of 4 to 6 years and after then increased again. CONCLUSIONS: We suggested that the boosting mumps vaccination will be required between the age of 4 to 6 years.