Glucosyltransferase serotypes a and g are closely related antigenically but are more distantly related to GTF of serotype c, based on assays of inhibition of total glucan synthesis. 2) Local immunization with GTF from serotype c S. mutans reduces the colonization, caries, and lesions caused by infection with the homologous strain compared with sham injected controls. 3) Local immunization with GTF of serotype c S. mutans reduces the colonization, caries, and lesions caused by infection with S. mutans of serotype g (strain 6715).