Many patients suffering from trauma or acute illness are in need of pain treatment in the prehospital phase, a treatment they seldom receive. In Denmark, it has been considered whether ambulance personnel should be allowed to administer pain treatment. Inhalation of 50% nitrous oxide and 50% oxygen has been administered for many years by non-physicians around the world. Therefore considerations concerning implementation of this treatment in Denmark are relevant. The aim of this paper was to evaluate the available knowledge about and experiences in using nitrous oxide outside the hospital for patients suffering from acute pain. The papers so far published are positive, but give no definite background for uncritical recommendation of prehospital pain treatment with nitrous oxide. There are no controlled studies concerning the effect of pain treatment in the prehospital phase. The few available controlled studies conducted inside the hospital have not shown significant pain-relieving effects of nitrous oxide for patients suffering from pain of acute medical of surgical origin when compared to other methods of pain treatment. Controlled studies of the effects of prehospital treatment with nitrous oxide need to be done. Technical problems and problems concerning indications, side effects, complications, pollution and possible addiction remain to be fully elucidated before prehospital treatment with nitrous oxide can be recommended for routine use in the Danish ambulances.