Studies were undertaken to assess the practice prerogatives of nonphysician clinicians (NPCs) in 10 disciplines that, collectively, are the major nonphysician contributors to the delivery of medical and surgical services. These disciplines include nurse practitioners, physician assistants, nurse-midwives, chiropractors, acupuncturists, naturopaths, optometrists, podiatrists, nurse anesthetists, and clinical nurse specialists. Marked differences were found in the practice prerogatives that states granted NPCs in the various disciplines. For most disciplines, the magnitude of their prerogatives correlated with the numbers of NPCs practicing in each state. At their maximal levels, state practice prerogatives authorized a high degree of autonomy and a broad range of authority to provide discrete levels of uncomplicated primary and specialty care. The recent growth in these prerogatives is fostering new opportunities for NPCs; however, it also is creating a pluralism that has the potential to further fragment the US health care system. It is time for regulatory integration and professional collaboration so that a health care workforce that includes a diversity of disciplines can be assured of providing a coherent set of patient care services in the future.