Paramedics in Oslo are allowed to make decisions about withholding or terminating cardiopulmonary resuscitation (CPR). In order to elicit the criteria used, 35 paramedics and nine doctors were interviewed after 70 episodes of cardiac arrest outside-of-hospital. CPR was not attempted in 21 patients, and discontinued in the field in 28 patients. Spontaneous circulation was restored in 15 patients, and six patients were transported to hospital with ongoing CPR. Both prognostic and ethical criteria were used without a clear borderline. Signs considered to indicate good prognosis such as VF, gaps, contracted pupils, or normal skin color always led to start of CPR. Bystander CPR was continued even when the professional thought the effort was futile, partly to encourage the bystanders. The social status of the patient did not affect the decisions, and advanced age only when combined with important criteria such as arrest times or the relatives' wishes. The only apparent difference between paramedics and doctors was that the reputation of the EMS system influenced only the paramedics. All paramedics had long experience which influenced their decisions, which were based on a rapidly composed broad picture of the patient's situation. All presented serious ethical considerations about life and death indicating that they did not make these decisions lightly.