People who have mental health crises while attending emergency departments require immediate assessment and management, and staff need to be prepared to meet the specific needs of this patient group. This article provides an overview of the Public Psychiatric Emergency Assessment Tool, which is used by Lancashire Constabulary, among others, to share information with healthcare professionals. By using the tool, practitioners can organise and structure the information they acquire during patient assessments, and from accompanying carers, paramedics or police. They can then pass this information on to specialist mental health professionals. This article was published previously in Emergency Nurse (2012) volume 19, number 10, pages 28-35, and was updated before publication in Nursing Standard.