This paper reports on one aspect of a larger grounded theory study exploring how nurses undertake the process of initial assessment at triage, specifically the process of 'initial visualisation'. Fourteen A&E nurses from two demographically distinct A&E departments were video-recorded undertaking a total of 38 live triage encounters. The recordings were replayed to the nurses who were asked to say what they were thinking at the time. The nurses' commentaries were recorded, transcribed and analysed using grounded theory methodology. The findings suggested that prior to the initiation of the triage encounter nurses had already assigned a general degree of urgency to the presenting problem. This was based on an immediate intuitive evaluation of 'the look of the patient', which comprised an assessment of 'obvious' physiological signs coupled with an appraisal of the degree of distress expressed. Nurses did this by dimensionalising client attributes and comparing those features considered salient to any given problem against an extensive repertoire of previous cases. The paper concludes by arguing that the process of 'initial visualising' is so central to triage that only research conducted in the actual clinical setting can truly elucidate the process of nurse reasoning.