AbstractIn Paris' 14th district (an urban community of 140.000), a pilot experiment has been carried out over a period of 10 years‐from 1976 to 1986‐directed toward the establishment of a coordinated, all‐embracing, very early prevention policy whose beneficiaries are the children who reside there, including even those from the very poorest families. This paper presents the various research‐action techniques that have been developed, especially those activities used by the United Childhood Section. This Section (S.U.E.) has permitted the institution of early preventive measures, as well as many new initiatives in the domain of practical preventive applications, and has allowed continual theoretical thought to spring from concrete activities. Through the participation of all kinds of social personnel who, for whatever reason, see any given child, it has been possible to reduce considerably the number of individuals who have contact with any one family; to reduce the total number of foster placements; to evaluate each kind of aide proffered; and, in every case, to respect the rules of infant mental hygiene. It has been possible to take preventive action truly early by refining well‐known clinical elements (neonate functional difficulties, maternal depression, etc.) and by intervening during pregnancy in lying‐in facilities, in neonate departments, in day‐care centers, and with mother's helpers.Two clinical and theoretically relevant cases are presented. One involves a classified list of risk indicators for different stages of infancy, and the other involves a validation in an 8‐year longitudinal epidemiological study of the mental health of 400 children identified during their first year by use of these very early indic