The objective of this study was to identify factors that influence emergency nurses' adherence to an emergency department national protocol (EDNP). A survey of emergency nurses (n=200) and physicians with medical end responsibility on an emergency department (n=103) was carried out. Emergency nurses' self-reported adherence to the EDNP was 38%, 55% of the nurses and 44% of the physicians were aware of the protocol. Interference with professional autonomy, insufficient organizational support and the EDNP's applicability were indicated as barriers for adherence. The main influencing factor seems awareness. Other factors related to the individual, the organization and to protocol characteristics. Solely disseminating the EDNP is not enough to get the protocol used in clinical practice.