This is the first of a two volume report on a Day Care Inventory designed to assess the day care child's understanding of his physical, social, and personal world. Theoretical and research literature on the development of the child, the available assessment techniques, and the results of an initial survey regarding day care objectives were the three major inputs used to determine decisions regarding what aspects of the child's cognitive, social, and emotional development were to be assessed. The present volume discusses the background and development of the inventory and describes the assessment staff and the sample of Pennsylvania day care children utilized in the field evaluation of the Inventory. Central to the report is a detailed discussion of the theoretical and research background for each of the 15 activities or components which were used in the Inventory for a direct assessment of each child. (CS)