A national survey showed that most insurance companies refuse to credential nurse practitioners as primary care providers in nurse-managed health centers. These prohibitive policies, along with weak federal and state laws, threaten the long-term sustainability of nurse-managed health centers as safety-net health care providers and limit the ability for nurse practitioners to become an accepted primary health care source in the United States. Interviews with national managed care organizations revealed that these companies' current business practice and policies are unlikely to change without regulatory change at state and/or federal levels.