Twenty-two anaesthetists participated in a study to assess the influence of occupational exposure to anaesthetic agents on mood (arousal and stress) and cognitive functions. In a cross-over design, each anaesthetist worked one day in a reference facility (for example, intensive care) and another day in a scavenged operating theatre where time-weighted exposure averaged nitrous oxide 58 p.p.m. and halothane 1.4 p.p.m. The results showed that arousal scores reached a peak in the middle of the theatre day, but this appeared to reflect the nature of operating theatre work rather than exposure. Reports of stress were also unaffected by exposure, although higher scores were associated with longer and more demanding work. Similarly, there was no evidence that exposure impaired performance of tasks assessing syntactic and semantic reasoning, verbal and spatial memory, sensory-motor reaction time and attention. Performance in these tasks was, however, sensitive to the cognitive demands of the tasks and to naturally varying non-exposure factors. It is concluded that, compared with the reference condition, the concentrations of anaesthetic agents found in actively scavenged operating theatres have no detrimental effect on either the mood or the cognitive functions of anaesthetists.