There is a growing concern among educators and policymakers about the level of attrition from Ph.D. programs in the sciences and humanities at some U.S. universities. Reliable estimates of graduate student attrition are difficult to obtain, however, because most information comes from the administrative records of individual institutions. This book provides a summary of datasets that could be used to analyze patterns of graduate student attrition and degree completion nationally, along with an analysis of recent studies on the subject. Based on this information, the committee examines the feasibility of designing a system to produce national estimates of graduate student attrition.