In the summer of 1969, Educational Testing Service (ETS) began identifying the 1,650 3 1/2-year-old children in four sites across the country who would become part of a six-year longitudinal study designed to assess the impact of Head Start. The sites were Lee County, Alabama, St. Louis, Missouri, Trenton, New Jersey, and Portland, Oregon. The children were measured on a large number of relevant variables before any of them had experience with some or no Head Start program. This report (the second of three) describes attempts to design an evaluative program based upon conceptions of the complexity of the human organism and an interaction model of human development. Six chapters present: (1) a short history of the ETS study, (2) impressions of the study communities, (3) measures used in initial assessments, (4) data collection procedures, (5) data storage and retrieval system, (6) plans for data analysis. The seventh and final chapter anticipates the activities of 1969-1970. Four appendixes are included: (a) tryouts of measure, (b) working papers, (c) the ETS-Head Start Longitudinal Study and the Westinghouse Study, (d) project personnel. Another part of this study is available as PS 003 657. (WY)