The first link in the 'chain of survival' is the activation of Emergency Medical Services (EMS). In the major part of Denmark, police officers operate the alarm 1-1-2 centre, including calls for EMS. Our aim was to study the police 1-1-2 operators' accuracy in identifying calls concerning patients with loss of consciousness as a key symptom of life-threatening conditions. 'Unconsciousness' was defined as patients with a Glasgow Coma Scale (GCS) score of or = 9, 972 of whom were reported 'awake', giving a specificity of 72%. The positive predictive value (percentage of patients found with a GCS score of