In order to expose disadvantaged preschool children to a variety of educational experiences and to health and social services, the New York State Legislature funded the State Experimental Prekindergarten Program (PreK). In 1975, a five-year longitudinal evaluation study was begun. The study has two major parts: (1) a general study of 5,800 students in 53 prekindergarten programs, continuing through the third grade, and (2) an in-depth study of 800 students in the early childhood programs of seven districts, also continuing through grade 3. The general study investigates the impact of program variations, particularly the number of contact hours, home vs. center based programs, extent of parent involvement, and teacher variables, on students with different cognitive and affective characteristics. The in-depth study documents, through systematic observation and record keeping, the continuity and characteristics of the preschool experiences. (MV)