Much of the literature on welfare dynamics has focused on the effects of recipient characteristics and state-level characteristics such as welfare benefits and economic conditions; there has been very little analysis on the effects of child support. This paper, using the 1979-1996 National Longitudinal Survey of Youth, examines whether child support affects the likelihood of leaving and re-entering welfare. The results indicate that strong child support enforcement is important in helping young mothers exit and stay off welfare. Women with $1000 child support payments in the previous year were 18 percent more likely to exit welfare and 12 percent less likely to re-enter welfare. Compared with women in states that pursued child support least vigorously, women in states that had passed extensive child support enforcement legislation and that spent more money on child support enforcement were 79 percent more likely to exit welfare and about 60 percent less likely to re-enter welfare. © 2002 by the Association for Public Policy Analysis and Management.