There is wide acknowledgement that apathy is an important behavioural syndrome in Alzheimer's disease and in various neuropsychiatric disorders. In light of recent research and the renewed interest in the correlates and impacts of apathy, and in its treatments, it is important to develop criteria for apathy that will be widely accepted, have clear operational steps, and that will be easily applied in practice and research settings. Meeting these needs is the focus of the task force work reported here.The task force includes members of the Association Française de Psychiatrie Biologique, the European Psychiatric Association, the European Alzheimer's Disease Consortium and experts from Europe, Australia and North America. An advanced draft was discussed at the consensus meeting (during the EPA conference in April 7th 2008) and a final agreement reached concerning operational definitions and hierarchy of the criteria.Apathy is defined as a disorder of motivation that persists over time and should meet the following requirements. Firstly, the core feature of apathy, diminished motivation, must be present for at least four weeks; secondly two of the three dimensions of apathy (reduced goal-directed behaviour, goal-directed cognitive activity, and emotions) must also be present; thirdly there should be identifiable functional impairments attributable to the apathy. Finally, exclusion criteria are specified to exclude symptoms and states that mimic apathy.