A British research study documented and defined the level of functioning of advanced neonatal nurse practitioners (ANNPs) in comparison with qualified nurses and junior pediatric medical staff working in the same neonatal units. Subjects were ANNPs, ANNP students, and clinician mentors in 10 units. Data were collected through interviews, questionnaire, diary or checklist, and observation. The role of ANNPs included the following tasks: deciding on patient admission, examining newborns, carrying out discharge examinations on the babies, providing emergency care, carrying out investigations, prescribing in accordance with guidelines, and teaching junior doctors and nurses. ANNPs saw their expanding role as appropriate professional development. Changes their expanded role brought included greater support for junior medical staff, better patient care, and improved communication. Students expressed a need for support, were satisfied with the theoretical input received, felt some areas were covered insufficiently, and enjoyed the learning experience. Clinicians raised the issue of funding and felt that classroom-based teaching had prepared the ANNP students very well. The majority of junior medical staff thought that all nurses should be taking on more as part of their job, but some felt threatened by the introduction of ANNPs. Conclusions were that misunderstandings about the role, problems of dual roles, and absence of sufficient funded ANNP posts made the transition to the role of ANNP difficult. (Appendixes contain 62 references and instruments.) (YLB)