Noting that the increase in the number, diversity, and needs of disadvantaged preschool-aged children poses potential obstacles to achieving the first National Education Goal that by the year 2000 all children in American will start school ready to learn, this document details the number and characteristics of 3- and 4-year-old preschoolers, and shows how the number and characteristics changed between 1980 and 1990. It also describes the differences in preschool participation rates for children by income level, age, geographic location, and other demographic characteristics. Composed predominantly of tables and graphs, the document presents the data by racial and ethnic group, linguistically isolated households (households in which no one 14 years of age or older speaks English"very well"), parental educational attainment, and parental employment status. The findings presented indicate that during the 1980s, the number of poor, near poor, and at-risk children most likely to face difficulties upon entering school, and who would have benefited the most from preschool programs, increased by 28 percent; the number of poor preschool-aged children increased in 46 states and became more concentrated in parts of the South and Southwest; and children in minority groups comprised about 57 percent of the poor preschool-aged population. (SM)