With the development of possible therapeutic interventions for people with dementia there is an increasing realisation among clinical and health service researchers of the paucity of appropriate outcome measures for people with dementia and their informal caregivers. The different perspectives on dementia within the biomedical, psychological and social models of disability lead to radically different meanings of the concept ‘quality of life’ and approaches to its assessment. This paper examines these different approaches and proposes a broad research agenda which is underpinned by two key principles. First, people with dementia and their informal caregivers should be involved in the development of usable outcome measures relevant to their needs and circumstances. Second, the scientific community in partnership with those directly affected should develop a pluralistic approach to the assessment of outcome taking account of both the meaning of the condition to people with dementia and their informal caregivers and cost utility from a societal perspective.