Are patients who are provided with details about anaesthesia risks on the eve of surgery better informed, and does the information increase their anxiety? Forty (ASA Class I or II) patients scheduled for surgery requiring general anaesthesia were randomly allocated to either a routine or a detailed information group. Levels of anxiety were assessed by the Spielberger State-Trait Anxiety Inventory. Actual knowledge of risks was assessed by a special visual analogue scale. Patients had experienced an average of five previous anaesthetics and so most patients in both groups knew the risks of common complications such as nausea and sore throat and were able to represent them accurately on the visual analogue scale. The detailed group, however, had gained more accurate knowledge of the likelihood of two rare complications, death (P < 0.001) and serious tooth damage (P < 0.05). Notwithstanding, there was no difference between the groups in anxiety. Thus, provision of detailed information about the risks of the complications of general anaesthesia did increase patients' knowledge but did not increase patients' levels of anxiety.