Effects of nitrous oxide in different subanaesthetic concentrations were studied in twelve subjects. Subjective scales of intoxication and of eight other mood variables were obtained by the method of magnitude estimation. Objective performance was examined by tests on memory and arithmetic. For most variables the dose‐response curves obtained showed progressively larger effects with increasing dose‐levels. At concentrations below 20 per cent the changes were, on the whole, very slight. The results are compared with similar data from an alcohol experim