The presence of undocumented migrants is increasing in many Western countries despite wide-ranging attempts by governments to increase border security. Measures taken to control the influx of immigrants include policies that restrict access to publicly funded health care for undocumented migrants. These restrictions to health care access are controversial, and evidence suggests they do not always have the intended effect. This study provides a comparative analysis of institutional, actor-related, and contextual factors that have influenced health care policy development on undocumented migrants in England and the Netherlands. For undocumented migrants, England restricts its access to care at the point of service, while the Netherlands restricts through the payment system for services. The study includes an analysis of policy papers and semistructured, in-depth interviews with various actors in both countries. Findings confirm the influence of such contextual factors as immigration considerations and cost concerns on health care policy making in this area. However, these factors cannot explain the differences between the two countries. Previously enacted policies, especially the organization of the health care system, affected the kind of restrictions for undocumented migrants. Concerns about the side effects of generous treatment of undocumented migrants on other groups played a substantial role in formulating restrictive policies in both countries. Evidently, policy development and implementation is critically affected by institutional rules, which govern the degree of influence that doctors and professional medical associations have on the policy process.