Demented elderly people often show severely fragmented sleep-waking patterns and are associated with disorganized circadian rhythm. Frequent nocturnal awakening and associated behavioral and psychological symptoms in demented people place a heavy burden on their families and care givers,and the development of an effective therapy is an important concern to health care practitioner and researchers. Although sleep disturbances in demented people could be classified into not only insomnia type but also irregular pattern type,differentiation has not yet been sufficiently practiced in a clinical setting. Demented people with irregular sleep pattern increase with progressive stage and are often insensitive to the usual pharmacotherapies for insomnia using benzodiazepines or antipsychotics. From the viewpoint of risk-benefit balance, chronotherapies such as artificial bright light or improvement of sleep hygiene could be useful and safety tools for sleep and behavioral problems in the demented elderly.