An investigation was carried out to see whether it was possible in nitrous oxide-oxygen anæsthesia to limit supplementation to a relaxant and to avoid entirely additions of central depressants. It was found possible in every case to secure an anæsthesia that was satisfactory to the patient, the surgeon and the anæsthetist. In fact the picture of this anæsthetic could not be distinguished from nitrous oxide anæsthesia, where supplementation with barbiturates and pethidine is used. It therefore seems as though this supplementation is mostly used to “cover” the weak effect of the gas during the saturation period and perhaps sometimes also to add to the effect of the gas when it is used at a lower partial pressure than in this series of cases. It was, however, also the impression that the use of the relaxant itself was part of the reason why other supplementation could be discarded. Yet, the amount of relaxant used was of the same order as when central depressants were employed. As a result of this study it is concluded that in suitable cases this method of anæsthesia should be taken into con sideration as a worthwhile alternative to other methods.