Previous techniques used for the detection and quantitation of antibodies in body fluids may be inappropriate where only small volumes are available, or may not be sensitive enough to detect low levels of specific antibodies. An indirect ELISA technique has successfully been employed to estimate class-specific antibody levels to Streptococcus mutans in serum and secretions in a group of mothers and their neonates, and an attempt has been made to relate such levels to the presence or absence of active caries in the mothers. A high maternal serum IgG antibody level appears to exert a protective effect against dental caries. Antibody levels in maternal saliva and colostrum/breast milk showed no differences between the 2 groups. The presence of active caries in mothers was associated with an elevated IgA antibody level in neonatal saliva. Although ELISA permitted the detection of low levels of antibody in the small volumes of neonatal saliva collected, a further increase in sensitivity and specificity of the assay would be advantageous.