This report is part of a comprehensive study of the cognitive, personal, and social development of disadvantaged children over the crucial period age three through grade three. The aims of the study are to identify the components of early education associated with children's development, to determine the environmental and background factors influencing such associations, and, if possible, to describe how these influences operate. The report focuses on: strategy and tactics in conducting research with the disadvantaged, children's cognitive and perceptual development, personal and social development, physical health and nutritional status, and the impact upon children of the family, the classroom, the teacher, the school, the community, and the tester. A summary of the measurement strategies and procedures, systems design and control, and the analysis of the longitudinal study complete the report. An appendix "a" discusses project personnel. A supplementary volume carries appendixes "b" through "f", relating to measures of classroom ratings of children's characteristics, of taxonomy of children's interest, and of contextual differentiations; encyclopedia of proposed measures, by title; index to proposed measures, by variable; and, selection of study sites. [Pages C-5, C-55, G-9, G-10, I-13, L-4, L-5, L-6, and L-7 of the text may not reproduce well because of the small size of the original type.] (RJ)