The time interval since previous anaesthesia was compared in a surgical population in South Wales and in patients who developed jaundice after halothane. There was a significant difference in the pattern of time interval since previous general anaesthetics in the surgical population and in those patients who developed jaundice after halothane. In the group who developed jaundice there was an "excess" of patients who had had a previous halothane anaesthetic within four weeks. Halothane should if possible be avoided in patients who have had it before, particularly if this was within the previous four weeks. In the case of repeat halothane anaesthetics within four weeks, the risk seems to lie between 1 in 6,000 and 1 in 22,000.