Most hospitalised injury cases have sudden onset at a specific time and date, due to a well-defined external cause (eg, a road crash). Date of injury is not presently recorded in routine hospital separations data in NSW or Australia, though it is in New Zealand. Benefits of adding date of injury to the Inpatient Statistics Collection would include: more accurate estimation of the population incidence of serious injury; better assessment of the health system utilisation and costs attributable to injurious events; and better linkage of hospital data with other data relevant to injury measurement and control (eg, road crash data).