The consequences for cognitive functioning of normal aging, depression and dementia are well known. However, the borderline between normal and pathological cognitive aging is less well understood. Recently, it has been found that it is important to differentiate between 'successful', 'usual' and pathological cognitive aging. This article reviews existing views on this borderline. Recently, it has been found that health-related factors, or biological life events, may determine the rate of cognitive aging. Various different, but similar, diagnostic descriptions of age-related cognitive dysfunction exist simultaneously: benign senescent forgetfulness, malignant senescent forgetfulness, age-associated memory impairment, age-consistent memory impairment, late-life forgetfulness, mild cognitive changes (subthreshold) and cognitive impairment disorders are some examples of different diagnostic categories. There are also various diagnostic tools to obtain these experimental diagnoses; for example, the Global Deterioration Scale, the Clinical Dementia Rating Scale and the Cambridge Mental Disorders of the Elderly Examination. A diagnosis is considered important for the early detection of dementia. Pharmacological treatments are still in the experimental stage. Improvement of cognitive function has particularly been studied in clinical trials with groups of patients with Alzheimer's disease as well as patient groups with age-associated memory impairment. Future strategies may orient more towards treating symptoms of cognitive dysfunction, probably also on the basis of diagnosis of health-related factors, in age-related cognitive decline and depression.