In a world shaped by global competition, preschool education programs play an increasingly vital role in child development and school readiness. There is growing awareness that early learning's impacts persist across children's life spans, affecting educational achievement, adult earning and even crime and delinquency. Preschool education is increasingly seen as a middle-income essential. In 2005, two-thirds of 4-year-olds and more than 40 percent of 3-year-olds were enrolled in a preschool education program. This represents a substantial increase over earlier decades, particularly at age 4. The evidence indicates the increase in enrollment has not reached all segments of the population equally and there are variations in participation rates regionally within the U.S. This report seeks to identify these important differences and shed light on how income, education, ethnicity, family structure, maternal employment and geography relate to preschool education program participation. (Contains 1 table, 10 figures and 21 endnotes.)