This publication, the first of two volumes, describes the cognitive, psychomotor, and socioemotional measures used in all years of the Head Start Planned Variation Evaluation. Part I discusses generally the issues involved in evaluating the quality of the data, and summarizes findings. Part II contains technical reports on 12 of the individual measures used in the evaluation, such as the Preschool Inventory and the Stanford-Binet Intelligence Test (which were considered especially useful), the Classroom Behavior Inventory, and the Brown IDS Self-Concept Referents Test. There is a description of each measure and the theory behind it, as well as a review of the available data on the measure's reliability, validity and other technical qualities. Judgments on the usefulness of the measures, and a summary of the information on which the judgments were based are presented. Data tables are included. (SET)