The UK National Institute for Clinical Excellence (NICE) is charged with the duty of providing informed guidance on clinical practice (clinical effectiveness and cost effectiveness) to patients and health professionals. The Appraisal Committee through its process of review of evidence advises NICE on the clinical effectiveness and cost effectiveness of new and existing technologies and their appropriate use within the National Health Service in England and Wales. The appraisal process takes into account both published and unpublished evidence as well as input from professional and patient and carer groups when coming to its decisions. The appraisal of a new technology often has to bridge the gap between the evidence required for licensing purposes and that needed to provide pragmatic advice to practising clinicians. The appraisal of zanamivir (Relenza) is an excellent working example of this difficult and important process.