In the pages that follow, I summarize and critique a growing body of literature on child care, Head Start, pre-K, and early childhood demonstration programs. I define these terms as follows: child care--regularly scheduled nonparental care for children of diverse ages that usually takes place outside the child's home; Head Start--a federally funded program for disadvantaged and disabled 4-year-olds and 3-year-olds that provides a variety of services to the child and the child's family; prekindergarten-- an educational program for 4-year-olds (and sometimes 3-year-olds) that is funded by the state government and often provided in a school building; and early childhood demonstration programs--relatively expensive experimental interventions in the lives of children, ages 0-5, that typically target "at risk" children. Inevitably, my review will be selective. But I have tried to pay attention to evidence on both sides of the big issues, where the evidence diverges. I have also tried to help the reader distinguish between more valid and less valid research and to recognize some of the public policy implications of the more valid research. The curious reader will find an even richer body of literature buried beneath the articles, books, and monographs highlighted here. (author abstract)