As a part of multipurpose health survey of the population in Vietnam the antibodies against S. typhi were determined by the micromethod using haemagglutination test (O-antigen 9, 12) and agglutination test using standard H-diagnostic antigen (d). Totally 292 sera were examined, 139 from Duyen Thai village and 154 from Mai Chau. The data on vaccination against typhoid fever are recorded only in 102 persons. The positivity on Vi antibodies is very high--70% in Duyen Thai and 47% in Mai Chau. This finding is significant according to the high titres in the carriers of S. typhi. The titres of all antibodies are lower in Mai Chau area situated in mountains then in crowded lowlands of Duen Thai. The level of antibodies is decreasing with age. The frequency distribution of antibodies by age proves endemicity of the disease in area, where a large part of population is infected already before reaching 20 years of age. The effectivities of vaccination is discussed.