Abstract: This study explores how registered nurses working within the acute surgical ward environment of a New Zealand hospital communicate changes in a patient's condition. The purpose of this research study was to examine the processes, communication techniques and behaviours that nurses use, in order to determine the critical requirements for registered nurses to effectively communicate changes in patients' conditions to doctors. The critical incident technique developed by Flanagan (1954) was adapted and used to explore incidents that occurred when six registered nurses working in acute surgical wards communicated a change in a patient's condition to a doctor. Communication is an integral part of everyday activity. This study has shown an assessment process occurs before communication can take place. A nurse's concern for a patient's condition initiates the assessment process. A judgement is formed from the nurse's concern that a patient's condition has changed. Judgements take into account multiple ways of knowing including pattern recognition, empirical knowing and intuition. Institutional protocols also affect judgements and the ability of a nurse to ensure support is received for the patient's well being. The communication process is initiated for two reasons, to support the patient, and to support the nurse in providing care for the patient. Significant in determining the need for support is the action required that might be outside the nurse's scope of practice. The response should address the nurse's concern and take into account the importance of the relationship, trust between all parties, respect of each other's positions and knowing team members and their capabilities. Understanding these aspects of the communication process should enhance nurses and doctors abilities to effectively communicate regarding a change in a patient's condition.