This chapter focuses on genetic testing for Alzheimer's disease (AD), as it is highly debated in the fields of gerontology and dementia care. Alzheimer's disease is the most common cause of dementia, but other important causes are Parkinson Disease, Frontal Lobe dementia, Lewis Bodies Disease. Alzheimer's Disease International estimated that 35.6 million people worldwide lived with dementia in 2010. It is controversial whether AD and dementia more generally, are part of the process of physiological ageing, or whether they represent a pathological state. Recent guidelines published by the largest world-wide patient advocacy organisations, the US-based Alzheimer's Association and the National Institute on Aging (NIA), define a new stage: preclinical Alzheimer's disease describes a stage in which biomarkers are measurable but memory and behaviour are not yet affected. A major research aim of the REVEAL study was to explore the interest in testing of potentially affected groups in North America.