Managed care is a process of health-care management that integrates financing, cost-containment strategies, and business principles with the delivery of health care. Managed care's rapid transformation of specialty practices, such as oncology, is redirecting classic nursing functions towards market initiatives that value the design of care/case management systems and the implementation of multidisciplinary "patient-centered" care models. As health-care systems continue to evolve, advanced practice nurses (APNs) are redefining their roles and enhancing their skills to meet the demands of the marketplace. Advanced practice nurses are defined as registered nurses who have met advanced educational and practice requirements and are prepared at the graduate level. This paper will identify the four established APN roles: nurse practitioner (NP), nurse anesthetist, nurse midwife, and clinical nurse specialist (CNS), as well as highlight the nurse practitioner and clinical nurse specialist as the leadership APN roles within oncology practice. The adaptation to managed care has identified new functions and created opportunities for these APN specialties that are being viewed both competitively by other oncology health-care providers and creatively by managed-care organizations. The integration of these emerging roles within the new advanced nursing market and their contributions to oncology care are also discussed.