So long as child support enforcement was entirely the legal domain of the states, it was nearly impossible to pursue claims across state lines, and interstate claims were characterized as the “black hole” of child support enforcement. The Uniform Interstate Family Support Act (UIFSA) clarified lines of authority, opened state IV-D agencies and courts to interstate claimants, and invented powerful new tools for pursuing cross-state claims. This paper uses Survey of Income and Program Participation data spanning the reform era to assess the success of this policy. The potential endogeneity of interstate moves with the policy regime may bias conventional regression estimates. A conditional difference-in-difference matching estimator is implemented instead. The findings indicate greatly increased administrative enforcement activity for interstate cases subsequent to UIFSA. This activity increased formal support agreements and identified greater amounts of support owed. There is also evidence of increased interstate collections and a closing of the ‘black hole’. Support collections increased especially for welfare-receiving households, but nonwhite households and households with nonmarital births do not appear to be helped by UIFSA.