The aim of this study was to describe the dispatch of emergency ambulance requests in Trondheim and to evaluate the medical justification of such ambulance missions. Data concerning 555 emergency ambulance missions were recorded from March to August 1986. A review of the cases shows that almost 40 per cent were unjustified. However, whether the ambulance missions were justified or not was significantly connected to the age of the patient and with the person requesting the ambulance. Missions requested by health care professionals and missions to elderly patients were the most justified ones. Furthermore, the mission was more justified in the case of internal medical problems than for surgical cases and trauma. We also discuss different ways of improving the use made of emergency medical services outside hospital.