Introduction: The reported incidences of out-of-hospital cardiac arrests (OHCA) in western countries vary considerably. According to the latest report from Danish Cardiac Arrest Database (DCAD) the incidence rate in Denmark in 2004 was 51/100,000/year. The report states however that this number is uncertain. As the first region in the country, North Denmark Region has introduced a prehospital electronic healthcare record (designated amPHI™) in all of its 50 emergency ambulances. We used data from amPHI™ to examine the incidence of OHCA in the region. Methods: We extracted patient data from the amPHI™ database from 1st May to 31st December 2006. We then identified the patients who met the criteria for OHCA set by the DCAD: “Situations to which an ambulance is called, and where either the ambulance-staff or others have performed chest compressions or given electrical defibrillation”. We stratified those patients according to whether they received first aid, the identity of the first aid provider and the initial cardiac rhythm as diagnosed by the patient monitor. Results: 18,666 patients where in contact with an emergency ambulance in the study period. Of those 296 (89/100,000/year) met the definition of cardiac arrest. 83 of those (28 %) received first aid. The first aid was provided by layman (68 %), physicians (11 %), nurses (11 %) and first-aiders (4 %). In 6 % the identity of the first aid provider was unknown. The majority of the patients (n = 177 (58 %)) had asystole upon ambulance arrival. 37 (12 %) had ventricular fibrillation, 32 (10 %) had other arrhythmias, 21 (7 %) had sinus rhythm and a single patient (0.3 %) had ventricular tachycardia. Conclusions: We have shown amPHI™ to be a valuable tool for accessing information about OHCA. By a stringent electronic registration we found a considerably higher incidence rate for OHCA, than documented by the analogue nationwide registry. Further we discovered a high rate of first aid to OHCA-patients. Finally our data showed a high occurence of asystolia in patients who met the official criteria for OHCA.