Data used in this study are based on information collected by the Bureau of Census, which canvassed 52,000 households. About 273,000 three-year-olds, 872,000 four-year-olds, and 2,724,000 five-year-olds were enrolled in preprimary programs in 1967. About 5.4 percent of the 3-year-olds, 15.6 percent of the 4-year-olds, and 45 percent of the 5-year-olds were from families with annual incomes under $3,000. Three- to 5-year-olds most likely to be enrolled in preprimary programs were those in families with annual incomes of $10,000 or more, in households with white-collar heads, in urban areas, and in the west. (DO)