AbstractSubjects (16 men and 16 women) breathing 30 per cent nitrous oxide in oxygen, or 100 per cent oxygen, were tested to see if the effects of nitrous oxide on memory varied with different types of auditory stimuli and memory‐testing procedures. The drug produced substantial memory impairments. These impairments were milder in forced‐choice recognition than in yes/no recognition and for certain stimuli (first names of each subject's close relatives), but were not influenced by several other variations in test procedures and stimuli. Additional assessments indicated that nitrous oxide produced numerous subjective effects including some that are characteristic of psychedelic drugs. Subjective rating scales of the kind frequently used in drug studies revealed sedation but not the other mood effects.