Neonatal nurse practitioners have been introduced into tertiary level neonatal intensive care units in the United States, Canada, and the United Kingdom in response to the increased survival rates of extremely low birth weight infants, the shortage of physicians, and the nursing profession's emphasis on development of advanced nursing practice roles. This brief review summarizes the recent research related to the facilitating and constraining factors that influence the role; the safety, effectiveness, and cost of the role; the impact of this role on other members of the health care team; and the satisfaction of those in the role.