Census 2000 enumerated 158.9 million people aged 30 & over living in households in the U.S., of whom 5.8 million (or 3.6%) were co-resident grandparents, defined in this report as living with grandchildren younger than 18. Among these co-resident grandparents, 2.4 million (42%) were also ¿grandparent caregivers,¿ people who had primary responsibility for their co-resident grandchildren younger than 18. Among grandparent caregivers, 39% had cared for their grandchildren for 5 or more years. This report presents information obtained from 3 questions on the Census 2000 long form about co-resident grandparents. Census 2000 was the first time that questions on grandparental caregiving have been included in the decennial census. Tables.