A sero immunity survey on measles virus infection among children under 5 years of age in Central Java province was conducted in three types of areas, namely : rural, urban and measles-virus endemic areas. The objective of the study is to obtain the basic data of immune status from children under 5 years of age in connection with mass vaccination program against measles virus infection in Indonesia. A total of 763 peripheral blood samples were collected in filter paper disc from children under 5 years of age divided into age structure. Antibodies titers in blood were measured by Haemagglutination Inhibition Test against measles antigen. The result showed that children of 7—9 months of age were highest in the endemic areas (17.6%), high in urban (7.7%) and none of the 13 children examined in the rural was infected. The maternal antibodies in infants of 0—6 months of age were highest in the endemic areas (35.3%) as compared to 4.3% and 10% in the urban and rural areas. In children of more than 10—11 months old, the antibodies against measles virus were highest in the urban (31%), high in endemic areas (23%) and low in rural (6.9%), whereas among the 2—5 years age-group, the antibodies level was about equal in both the urban and endemic areas, but lower in the rural area.