AbstractOutpatients attending for conservative dental treatment were presented with eight instructions which they were asked to remember. The instructions were either written or spoken, and were in a positive or negative form. Patients treated with nitrous oxide remembered fewer instructions than those treated with local analgesia alone, and this effect of nitrous oxide was particularly marked for written instructions. Patients receiving local analgesia alone were more likely to remember positive than negative instructions in their original syntactical form, but this bias was not evident in the nitrous oxide group. In a second experiment both normal and dentally phobic patients were read dental and general instructions both before and during inhalation of 30 per cent nitrous oxide. Both groups showed a nitrous oxide‐induced reduction in partially recalled instructions. There was interesting evidence for a different attentional bias in our two patient groups. The normal group remembered more general than dental instructions, whereas the phobic group showed the opposite pattern, yielding a significant patient group × type of instruction interacti