The Child Health and Development Studies are prospective longitudinal studies on medical and social aspects of pregnancies and on the health and development of children. Data have been assembled on about 20,000 pregnancies occurring in one hospital between 1959 and 1967, and on follow-up of the children through adolescence. A currently ongoing project updates certain vital statistics of the entire study population. The data assembled in this longitudinal study supported a wide range of research projects, several of which proved to be important for the health of mothers and children. Notwithstanding, subsets of the assembled data, with potential value for public health, have not yet been explored. The data archive has been made accessible to the research community at large so that other significant research topics can be investigated. In the following article, brief descriptions are given of the history and design of the Child Health and Development Studies, of the contents of the data archive, and of the major areas of research that have been explored. Procedures to obtain access to the data and to the user's manual are explained, and a bibliography is included.