Fifty women were examined after delivery for the prevalence of antibodies to human cytomegalovirus in colostrum and sera. Eighty percent of them had specific CMV IgG antibodies in the sera, as determined by the immunoperoxidase antibody to membrane antigen (IPAMA) technique. Of the CMV-seropositive women, 60% had specific CMV IgA antibodies in high titer in the colostrum as determined by enzyme-linked immunosorbent assay (ELISA). In only two of the seropositive women were specific CMV IgA antibodies detected in the sera as well. The significance of specific CMV IgA antibodies in colostrum as protection against perinatal infection and the mechanism of this production will be discussed.