The Personal Responsibility and Work Opportunity Reconciliation Act of 1996 directs the Census Bureau to measure the effects of welfare reform. To carry this out, we are conducting the Survey of Program Dynamics (SPD), a large longitudinal, nationally-representative survey. It is designed to provide information on intervals of actual and potential program participation over the ten-year period 1992 to 2001 and to examine the causes of program participation and its long-term effects on the well-being of individual recipients, their families, and their children. We will describe the survey, address the Census Bureau's plans to construct a consistent, longitudinal data series from three distinct survey instruments, and then describe how the data are to be used for research purposes. Finally, a brief description of other welfare-related data sources is presented, including a discussion of how national and state data can be used to supplement each other.