ABSTRACT. The concentration in human milk of IgA antibodies against six Salmonella and two Shigella groups was determined in specimens obtained from Swedish and Guatemalan nursing mothers of three different socioeconomic levels. The daily intakes of milk antibodies by their children were also estimated. The results show that the concentrations of specific IgA antibodies in milk vary among the different population groups. There is, however, no difference in daily intake of specific IgA by the children.