Based on U.S. national (N = 2673) and central cities (N = 8263) probability samples, this paper: (1) presents estimates of the proportion of the United States population that has provided informal care to persons with AIDS; (2) identifies socio-demographic characteristics of 'typical' AIDS caregivers in the U.S.; and (3) discusses social, economic and health-related implications of informal caregiving to persons with AIDS. Results indicate that 5.0% of all adults age 18-75 living within central cities and 3.2% of the entire adult U.S. population have provided care to a friend, relative or lover with AIDS. Although caregivers are distributed throughout different age and ethnic groups, the majority of caregivers are younger (< 40 years) and white. Males, gay and bisexual men in particular are over-represented among central cities caregivers. Data on the types of caregiving tasks performed show that 64.4% of all caregivers within central cities perform domestic types of caregiving tasks, while 27.7% are involved in personal care of AIDS patients. Caregivers are more likely than non-caregivers to have been tested for HIV, and among the tested, caregivers are more likely to have tested positive. While informal caregiving reduces costs to the formal medical sector, costs to the caregivers themselves should be considered. Physical and emotional stress, as well as reduced opportunity for social and economic development, represent potential outcomes of caregiving. Socio-demographic characteristics of AIDS caregivers, such as their typically young age, suggest that these caregivers may be at particular risk for detrimental consequences.