The growth of the undocumented immigrant population in the United States has been explosive. The absence of a uniform policy regarding health care for this population has created a unique problem for nephrologists. How should provision of care for undocumented immigrants with end-stage renal disease be delivered and compensated? This problem is exacerbated by the multiple complex laws that govern delivery of and payment for care, as well as that state regulations vary widely and are not easily understood. Furthermore, the ethical and moral commitments of providers to ensure adequate and appropriate care for any patient whose life is at stake, irrespective of his or her immigration status, place nephrologists in a difficult position. This review focuses on the scope of this problem, relevant case law and legislation, current care and payment models, the response of nephrology groups, and ethical dilemmas inherent in caring for this vulnerable population. Recommendations for further study, including convening of a consensus conference, are discussed. Copyright 2009 National Kidney Foundation, Inc. Published by Elsevier Inc. All rights reserved.