"Triage" is a useful tool used in emergency departments (EDs) to prioritize the care of patients. Through a methodical process of different sequential steps, the triage nurse assigns a color code which goes from red-critical patient with immediate access to medical examination-to a white code that represents no urgency. Clinical studies have shown that patients can be victims of errors during the process of care, especially in complex systems such as EDs. To reduce errors it is essential to map the risks in order to identify the causes (both individual and organizational); the introduction of corrective changes cannot be postponed. The incorrect assessment at triage represents one of the major errors in EDs. By monitoring this activity, through the analysis of sentinel events we can reduce adverse consequences. Missed recognition of a red code indicates a sentinel event. We used a "root cause analysis" to explain an episode of missed recognition of red code at triage. A nurse without specific training in triage and inexperienced in critical care was identified as the "root cause" of the sentinel event. To make improvements we planned a triage training course (for newly employed nurses and a refresher course for existing staff) and created a team of dedicated triage nurses.