Because of their unique social, legal, and political status, American Indians and Alaska Natives are subject to legislative oversight unlike any other group in the United States. Census data are used to monitor the size and characteristics of the American Indian and Alaska Native population living on and off reservations. Passed in 1978 to ensure tribal self-determination in matters related to family preservation, adoption, and child custody, the Indian Child Welfare Act raised thorny issues concerning racial identity and tribal membership. In the 2000 Census, respondents were instructed to mark all races that applied to their racial identity. Historically, American Indians have had high rates of intermarriage with other groups, so a relatively large number of Native children identify with multiple racial groups. Comparing the numbers of American Indians and Alaska Natives reported in the 2000 Census with those from earlier censuses is problematic, because there are now two sets of numbers for comparison. Between 1990 and 2000, the number of Native children increased by 21 percent (using the single-race definition), or by 99 percent (using the multiple-race definition). Overall, 1.4 million children were identified as American Indian in the 2000 Census. The number who reported only one racial group was 840,000. Census data report self-identified American Indians, resulting in a significant mismatch between the census numbers reported by the Census Bureau and the numbers considered eligible for tribal membership. In 2000, approximately 29 percent of all Native children lived on reservations or in Alaska Native villages. Only Native ancestry was reported for the overwhelming majority of children on reservations (87 percent). Tables present data on the Native population under age 18. (TD)