The rapid evolution of health care delivery within the United States has created increased opportunities for nurse practitioners (NPs) to work in a variety of challenging advanced practice roles and to impact the quality of health care. The NP role was originally developed to meet a perceived shortage of primary care physicians, especially for underserved populations. Today, NPs work in various fields, such as geriatrics and women's and family health care, as well as in various systems such as private practice and health maintenance organizations. Effective collaboration with physician colleagues will promote improved communication, health care management, and positive health outcomes. Barriers to effective collaboration are reimbursement, territorialism, and role confusion on part of the health care team and the general public.