This monograph presents a detailed description of the background, design, methods, and subjects of a study of sex-role socialization in the nursery school. The objectives of the study were to (1) define sex-role differentiation, (2) examine the relation between age and sex-role differentiation,, (3) describe and explain the influences of the nursery school and of personal, socioeconomic, and familial characteristics on sex-role differentiation, and (4) provide much needed longitudinal data on sex-role differentiation during the preschool years. Using an incomplete cohort-sequential design, the researchers followed more than four hundred 3-, 4-, and 5-year-old boys and girls for all or part of their nursery school careers. Within each age level, the classes were equally divided between lower an midddle income level schools. The children were pretested and posttested each year on five measures of sex-role development and one measure of intelligence. Additionally, the child-teacher, child-child, and teacher-child behaviors were observed at 2- to 3-week intervals in the naturalistic environment of the classrooms. Complete data from testing and observations are included in the monograph. Results are not discussed. (Author/JMB)