The number of day care centers and home care facilities has steadily increased in the United States. Recent interest has focused on the possible relationship between attendance at child day care facilities and the occurrence of certain infectious diseases. A variety of infectious agents have been reported as causes of illness among children and staff in day care programs. In general, however, concurrent risks for these infections among children attending and those not attending day care programs have not been established by prospective studies. A review is made of the pathogens that have been associated with infections in day care settings, patterns of occurrence of infectious diseases in day care facilities, aspects of control and prevention of these diseases, and controversies related to infectious diseases in child day care facilities. Aspects of this problem that warrant further research are outlined.