["Sociology of Health & Illness, EarlyView. ", "\nAbstract\nTheories of physician dominance are a foundational contribution of medical sociology to the study of health care, but must be revisited in the light of ongoing changes in medicine. As non‐physician specialists like nurse practitioners grow in number and acquire more autonomy, increasing medical profession differentiation presents a challenge for traditional physician dominance theories. After evaluating potential theoretical explanations for subordinate occupations' autonomy gains, we conduct a state‐level quantitative analysis of variation in nursing policies across U.S. states. We construct our dependent variable, nursing autonomy, using seven state‐level advanced practice nursing policies adopted from 2001–2017. Using an ordered scale, we code nurse practitioner, nurse anaesthetist, nurse midwife and clinical‐nurse‐specialist practice and prescription polices according to each policy's autonomy level. We then use time‐series regression to examine theory‐driven propositions regarding nursing autonomy change. Nursing autonomy has increased over time, signalling a general erosion of physician dominance. However, we find differential patterns of policy adoption, indicating that erosion is not uniform. Physicians have maintained dominance in relatively prestigious specialties (e.g. anaesthesiology) while dominance declined in others (e.g. obstetrician). Factors external to the profession, such as consumer power, continue to influence within‐profession dynamics. Examining ongoing professional differentiation in medicine illustrates how physician dominance depends on shifting social and professional contexts.\n"]