A confidential survey was conducted among medical practitioners in New Zealand with a stated interest in anaesthesia to ascertain the proportion of those currently engaged in anaesthetic practice (thought to be approximately 325), who knowingly omit or alter undesirable physiological parameters from the anaesthetic record. Two hundred and forty-five replies were received from currently active anaesthetists. The reported frequency of occasional data omission or falsification was 55%. Those anaesthetists who intentionally manipulated data were more likely to be dissatisfied with their current anaesthetic record form, to view the record as an intraoperative distraction and less likely to perceive the record as being important for the use of future anaesthetists. There was no correlation between data manipulation and concerns over the medicolegal uses of the record.