The percentage of Taiwanese aged 65 years and older has been increasing over the past 27 years, from 4.1% in 1980 to 10.2% in 2007. Studies on the Taiwan population have shown that the prevalence of dementia is approximately 1.7 - 4.3% among aged people, and that the most common cause of dementia is Alzheimer's disease (AD). However, compared to Western countries, this is a low prevalence rate, which might be due to the simple lifestyle led by aged Taiwanese, a selective higher mortality rate in Taiwanese, and a low prevalence of the APOE4 allele in Taiwanese. The current evaluation of dementia in Taiwan derives from several reliable and valid cognitive and behavioral assessment tools originally developed in Western countries. These tools are not only useful for clinical evaluation, but also have offered a method for possible cross-cultural assessment. Behavioral and psychiatric symptoms of dementia in Taiwan have been shown to be similar to other ethnic groups, except for a relative high prevalence of apathy. Although three cholinesterase inhibitors and one glutamate NMDA receptor antagonist are available in Taiwan to treat dementia, their insurance reimbursement is strictly regulated and only a small proportion of patients with AD receive medical treatment. A local consensus of and guideline for diagnosis and treatment of dementia is needed in Taiwan.