Title. Thinking strategies used by Registered Nurses during emergency department triage Aim. This paper is a report of a study to describe and compare thinking strategies and cognitive processing in the emergency department triage process by Registered Nurses with high and low triage accuracy. Background. Sound clinical reasoning and accurate decision‐making are integral parts of modern nursing practice and are of vital importance during triage in emergency departments. Although studies have shown that individual and contextual factors influence the decisions of Registered Nurses in the triage process, others have failed to explain the relationship between triage accuracy and clinical experience. Furthermore, no study has shown the relationship between Registered Nurses’ thinking strategies and their triage accuracy. Method. Using the ‘think aloud’ method, data were collected in 2004–2005 from 16 RNs working in Swedish emergency departments who had previously participated in a study examining triage accuracy. Content analysis of the data was performed. Findings. The Registered Nurses used a variety of thinking strategies, ranging from searching for information, generating hypotheses to stating propositions. They structured the triage process in several ways, beginning by gathering data, generating hypotheses or allocating acuity ratings. Comparison of participants’ use of thinking strategies and the structure of the triage process based on their previous triage accuracy revealed only slight differences. Conclusion. The wide range of thinking strategies used by Registered Nurses when performing triage indicates that triage decision‐making is complex. Further research is needed to ascertain which skills are most important in triage decision‐making.