Complaints of poor memory are common in the healthy elderly and to many it may seem unsurprising that cognitive function declines with ‘normal’ ageing. Virtually every biological system alters with age and, just as a 70-year-old cannot run as fast or hear as well as when he or she was 20, it is perhaps inevitable that cognitive function also becomes impaired. However, far from being straightforward, the nature, classification and clinical significance of age-related cognitive changes that fall short of dementia remain a most controversial and difficult area (see O'Brien & Beats, 1994; Dal Forno & Kawas, 1995). The recent emergence of new drugs for the treatment of Alzheimer's disease (donepezil and rivastigmine) and related disorders has emphasised the need to study groups with milder degrees of cognitive impairment. It is necessary to determine whether such conditions are benign and non-progressive, or harbingers of progressive dementia and so appropriate conditions to target for early therapeutic intervention. The presence of age-related cognitive changes raises other important issues including why such changes occur, how they should be classified and whether, even if ‘benign’, they can and should be treated.