The importance of delirium as a component of cognitive impairment is well known to the readers of this journal, but little is known of the true incidence in the community. Accurate diagnosis of delirium used to require specialist input, but two years ago, in this journal, Richardson et al.(2017) demonstrated the reliability and specificity of a“combined arousal and attention testing procedure”for detecting delirium superimposed on dementia in hospital inpatients, where the patient is physically present. The paper by Luijendijket al.(2019) in this journal takes this process two steps further with a questionnaire for caregivers. Two steps because,firstly, it has been validated for delivery over the telephone, and secondly, the input from usual caregivers provides a valuable additional perspective on what has changed about a patient.