This study of 150 individuals, 85 years and older, focused on their families and social networks. Using both structured and open-ended questions, we explored the extent to which the family functions as a source of support for the oldest old. The findings indicate that those with children are significantly more active with all relatives, most likely because children link them to grandchildren, great-grandchildren, and their relatives by marriage. For the 30 percent who are childless and unmarried, other relatives are not usually active providers of support, a finding which suggests that the principle of substitution does not operate effectively for this age group. Case studies illustrate the variations in family functioning in the support of their oldest members