OBJECTIVES: To estimate the rate of unintentional drowning mortality and hospitalised morbidity using population-based, population-risk and person-time denominator data and to compare the estimates obtained. To then compare exposure-based rates for drowning with road traffic death rates. METHOD: Retrospective analysis of unintentional drowning mortality and hospitalised morbidity of New South Wales (NSW, Australia) residents 16+ years of age during 1 January to 31 December 2005. Information on population-risk and person-time risk was obtained from the 2005 NSW Population Health Survey. Analysis of road traffic death data from NSW and population and person-time risk estimates from the Survey of Vehicle Use, Household Travel Surveys and Roads and Traffic Authority Speed Surveys in 2005. RESULTS: Estimated drowning mortality and hospitalised morbidity rates for adults were higher using population-risk and person-time risk exposures compared to a population-based exposure. Population-based estimates of road traffic mortality were four times higher than drowning mortality rates. In contrast, exposure adjusted person-time estimates for drowning were 200 times higher than road traffic fatalities. CONCLUSIONS: Many injury risks are underestimated when the total age-specific population is used to calculate an injury rate instead of actual population-risk or person-time exposure. This can result in the identification of misleading priorities for injury prevention. Drowning risk is strikingly higher than previously thought based on population-based estimates. This information is important for decision-making and policy development as it provides a basis for comparing the inherent risk in exposure to hazards with potential to cause injury.6 page(s