The expansion of health insurance coverage through health care reform, along with the aging of the population, are expected to strain the capacity for providing health care (1–3). Projections of the future physician workforce (4,5) predict declines in the supply of physicians and decreasing physician work hours (6,7) for primary care (8–10). An expansion of care delivered by nurse practitioners (NPs), certified nurse midwives (CNMs), and physician assistants (PAs) is often cited as a solution to the predicted surge in demand for health care services and calls for an examination of current reliance on these providers (11,12). Using a nationally based physician survey, we have described the employment of NPs, CNMs, and PAs among office-based physicians by selected physician and practice characteristics.