The value of a primary nursing care delivery structure remains undecided. This study was carried out on an acute psychiatric admissions unit as it changed its care delivery system to that of primary nursing. A review of the literature highlights the inconclusive nature of previous investigations. The principle of evidence-based practice raises the need for further research to put this issue to rest. The staff perception of this change on both the atmosphere of the ward and on the role of the nurses themselves was analysed. A general reduction in satisfaction with role was discovered, as was a reduction in eight out of 10 subscales of the Ward Atmosphere Scale (Moos 1989). As primary nursing generally receives favourable reviews by nurses, and was in fact positively received by the staff in this study at the time of initiation, this negative result is surprising. It is conjectured that primary nursing may be an ideal philosophy of nursing that is difficult to realize due to constraints surrounding contemporary nursing practice.