Measurements of seven self-reported emotional states (happiness, activity, fear, anger, depression, fatigue, and anxiety) and three physiological variables (heart rate, systolic blood pressure, and diastolic blood pressure) were made among 16 subjects under four conditions: all subjects breathing normobaric air; several days later, immediately after half the subjects had breathed 30% nitrous oxide and the other half had breathed nomobaric air; the following day, subsequent to exposure of all subjects to a simulated depth of 57 m on air in a hyperbaric chamber; and several weeks after the hyperbaric chamber exposure, with all subjects breathing nomobaric air. The results showed that the physiological responses of the group that breathed nitrous oxide did not differ significantly from the control group following the hyperbaric chamber exposure, while self-reported happiness was lower among the nitrous oxide group than among the control group following hyperbaric chamber exposure. Nitrous oxide does not appear to benefit emotional or physiological adaptation to nitrogen narcosis associated with breathing hyperbaric air, and may even impair emotional adaptation, at least under these experimental conditions.