Does opening the door to US citizenship for unauthorized immigrants cause out-of-control “chain migration”? We address this question using variation from the legalization programs of the Immigration Reform and Control Act of 1986 (IRCA). Exploiting IRCA’s introduction and differences across metropolitan areas in program intensity, we estimate that each IRCA-legalized Mexican was responsible for the subsequent immigration and legal admission of one relative, in total, through 2019. Most sponsored relatives were immediate family, and the adult sponsorship rate is inconsistent with out-of-control chain migration. Estimates using cross-country variation are substantively similar and suggest limited demand for reunification of extended families.