This study of patient and bystander responses to medical emergencies revealed serious shortcomings in the public's ability to respond appropriately to such situations. Decision delays at least as long as ambulance response delays were found to be the result of confusion regarding the seriousness of the emergency, confusion regarding the appropriate reaction to the emergency, and a reluctance to burden the rescue service unnecessarily. A significant group of high-risk patients were identified who not only reacted slowly but who bypassed the emergency ambulance service entirely. A substantial fraction of these patients have had prior contact with the local medical care system for problems related or identical to the one causing the emergency.