Illegal Mexico-U.S. migration has increased dramatically in recent decades. In this article, Pia Orrenius evaluates the causes of this migration and gives an overview of the enforcement and policy responses to date. Orrenius assesses the effectiveness of border enforcement by looking at developments in the smuggling industry, such a smuggler use rates and fees, as well as changes in border-crossing sites. The findings suggest early attempts at enforcement fueled an increase in the demand of and supply of smugglers, with no rise in prices. Only the most recent enforcement initiatives, most significantly Operations Hold-the-Line and Gatekeeper, have been successful in reversing the thirty-year decline in smugglers' fees and moving migrants to remote crossing points. Risks have risen along with smugglers' fees, as reflected in an increasing number of crossing-related deaths since 1995. Orrenius concludes that Mexican and U.S. policymakers should consider a bilateral labor and migration agreement.