This article examines nurse practitioners' (NPs) professional autonomy as a critical component of future practice success and survival. Professional autonomy provides the basis for defining and negotiating NPs' work and worth in primary care. Outcome data and analyses that delineate the unique and overlapping practice roles and responsibilities of physicians and NPs will help determine the relative value of their work. Nurse practitioners practicing as physician “substitutes” risk professional survival. Nurse practitioners need to identify nursing as their practice paradigm and nurses as their professional identity.