This study evaluated the effect of a Head Start program on children's intelligence and reading achievement test scores over a three year period. Each of 25 Head Start children was paired with a non-Head Start child of the same reace, sex, age, socioeconomic status, date of school entrance, kindergarten experience, promotion record, and type of school. The second part of the study involved a three year followup assessment of intelligence test scores of children who had attended Head Start before entry into school. The conclusions was reached that Project Head Start had been effective in preparing children for later reading achievement, as determined by the word meaning subtest of the Stanford Achievement Test. The durability of this effect was demonstrated over a three year span. Intelligence, as measured by the Stanford-Binet Intelligence Test, improved during the longitudinal study, but the preschool program could not be given credit for the positive change. The author recommends continued longitudinal research in preschool compensatory education. (Author/WR)