OBJECTIVES: Bronchiolitis is a disease of the lower respiratory tract with peak incidence in the winter.  It is the leading cause of hospitalization during the first year of life and a major cause of morbidity and mortality. The estimated cost of the Victorian bronchiolitis hospital admissions for 2006 was $8.1 million dollars.  Nasogastric hydration (NGH) and intravenous hydration (IVH) are two techniques for fluid replacement therapy, required in approximately 20% of children admitted with bronchiolitis, however there is a lack of agreement on which method is most beneficial.  METHODS: The study was a multi-centre, three-year, open, randomized trial comparing NGH and IVH in children between two months and 12 months of age who were admitted to hospital with bronchiolitis and required non-oral fluid rehydration.  The setting was seven hospitals in Australia and New Zealand between 2009 and 2011. The primary outcome was ‘length of hospital stay’, with secondary outcomes covering ‘intensive care admission’ (ICU), ‘adverse events’ (AEs) and ‘number of attempts at insertion’. An economic evaluation was conducted alongside the trial to assess which approach is more cost-effective, as judged by their net ‘cost per child ready for discharge’ ratio. Each study site collected cost data covering treatment activities and outcome data including medical interventions, mediation received, complications, need for ICU admission and level of respiratory support.  The reference year was 2009. RESULTS: A total of 759 infants were randomised: 378 to IVH and 381 to NGH.  There was no statistically or clinically significant difference in the mean length of stay, ICU admission or AEs between treatment groups.  Success at insertion on first attempt was higher in NGH (85.1%) compared to IVH (56.1%), p<0.001. CONCLUSIONS: The full results of the economic evaluation will be presented. With no significant difference in outcomes the economic analysis was reduced to a cost-minimisation study.