In this article we explore methods for using mothers' interviews to gather data on their children's family formation experiences. These methods constitute a cost-efficient means of gathering data for models of family background that include both intergenerational and sibling influences. To judge the utility of these methods, we examine the quality of mothers' reports across a range of their children's family formation behaviors. The dimensions of reporting quality we analyze include completeness, precision, and accuracy of mothers' reports. We use unique data from personal inter-views with mother-child pairs to test the accuracy of these mothers' reports. The results demonstrate that, with some behaviors, a flexible data collection approach can gather complete, precise, and accurate information on an entire sibling set by interviewing mothers. Our examination of data quality also suggests important limits on the use of this approach. The quality of mothers' reports depends on the subject matter, with mothers providing lower quality reports of their children's cohabitation behavior compared to their children's marital, childbearing, and divorce behavior. (C) 2002 Elsevier Science (USA).