"Adult foster care" is a label that has been applied to very diverse programs. Although adult foster care appears to be a potentially important element in the continuum of care for older adults, its assumptions and characteristic features have not been clearly explicated. In this paper, common assumptions underlying adult foster care are suggested, representative adult foster care programs are examined, and persisting issues discussed. The results suggest that, as yet, there is no consensus among practitioners as to what are reasonable goals for adult foster care, who should participate in such programs, and what constitutes evidence of program success. Until these issues are resolved, adult foster care is likely to remain an underutilized form of long term care for older adults.