A prospective study was performed that allowed a quantitative estimation of blood loss in excision and grafting of adult burn injuries. The average value for blood loss was 9.2 per cent of the patient's estimated blood volume or 387 ml per 1 per cent burn excised and grafted. There was no exponential increase in blood loss as the percentage excised and grafted increased apart from proportionality and there was no statistical difference between males and females for burns excised and grafted days 1-14 after injury or greater than 14 days after injury. It was therefore concluded that a useful working figure is 400 ml whole blood or 10 per cent of patient blood volume is lost per 1 per cent full thickness burn excised and grafted for an adult. These values do not apply to the very young, the very old and those patients who have bleeding disorders, and when using various methods to limit blood loss. This figure allows adequate cross-matched whole blood to be available preoperatively.