BACKGROUND: The importance of interdisciplinary collaboration has been attested to by a number of authors. Some have suggested that Nurse Practitioners (NPs) may be able to improve collaboration between doctors and nurses, but this assertion does not appear to have been researched. AIMS AND OBJECTIVES: To investigate doctors' and nurses' perceptions of interdisciplinary collaboration in two neonatal intensive care units, and to assess the impact of a Neonatal Nurse Practitioner (NNP) practice model on these perceptions. The study was conducted as part of a larger project to develop a NNP model of practice. DESIGN: Survey, pre- and post-intervention. METHODS: Medical and nursing staff in both units were surveyed before and after introduction of the NP model of practice. The instrument consisted of 25 statements relating to nurse-doctor interactions, with which respondents indicated their level of agreement on a five-point Likert scale. The Mann-Whitney U-test was used to compare scores for individual items and for overall collaboration between various groups of staff, and between the first and second surveys. RESULTS: Significant differences between the responses of nurses and doctors were found on both surveys. Areas of disagreement chiefly concerned doctors' behaviour and their attitudes towards nurses, rather than nurses' behaviour or environmental factors. Doctors consistently reported a higher degree of collaboration than did nurses. Few differences were found between first and second surveys. CONCLUSIONS: Results suggest that problems in nurse-physician interactions exist in both units. No impact of the NNP role, as established in this project, on interdisciplinary collaboration could be demonstrated. Further research in this area is warranted.