Current reporting of hospitalisations from H1N1 influenza includes little patient-level clinical data. An anonymised registry based at Monash University, Melbourne for patients admitted to intensive care in New Zealand and Australia with influenza was established in June 2009. Important insights into the clinical characteristics of critical illness due to H1N1 influenza infection have been identified and published. More detailed analysis of patients requiring extra-corporeal membrane oxygenation and cases associated with pregnancy have been undertaken. Specific data from the New Zealand cohort has also been made available to the Ministry of Health and the World Health Organisation. This proposal is to support the continued NZ contribution to the registry, at least until the end of winter 2010, to enable reporting and analysis of intensive care patient characteristics during any further re-emergence of pandemic influenza. This will be particularly valuable in characterising the pattern of critical illness in a vaccinated population.