Abstract: Objective: To calculate the minimum prevalence of malnutrition among rural Aboriginal children under two years of age in the Top End of the Northern Territory (NT) using World Health Organization (WHO) criteria. Methods: We calculated weight-for-height and height-for-age Z-scores (WHO-endorsed references) for all children under two years who were admitted to hospital with diarrhoeal disease between May 1990 and April 1991. Weights recorded 48 hours after admission were used to allow for acute dehydration. Malnutrition was defined in terms of ?wasting? and ?stunting? when weight-for-height and height-forage were more than two standard deviations below the median of the WHO reference population. The denominator population was calculated from NT Department of Health and Australian Bureau of Statistics data. Results: From an average population of no more than 480 children under two years, 34% were admitted to hospital at least once with diarrhoeal disease in the 12 months; 59% were malnourished (wasting alone, 36%; stunting alone, 10%; both, 13%). In the study period an estimated minimum of 20% of all Aboriginal children in the Top End were malnourished (wasted, 12%; stunted, 3%; both, 5%). Conclusions: The 20% prevalence of malnutrition is many times higher than would be expected statistically and higher than in many underdeveloped countries. International relief agencies regard a prevalence of wasting in children of more than 8% as a nutritional emergency. We urge that programs to alleviate the poor socioeconomic conditions, and mechanisms for early detection and intervention in childhood malnutrition, be offered to Aboriginal communities.