A community survey of dementia was conducted on a Chinese islet. A total of 221 men and 234 women in the age range of 50–92 were assessed. The Cognitive Abilities Screening Instrument (CASI), a 100-point cognitive test designed for cross-cultural studies and adapted in Chinese for individuals with little or no formal education, was administered twice by trained field workers with a retest interval of 3 to 4 weeks. In addition, all participants were assessed by physicians who did not know the CASI scores. The physicians' assessment included a complete neurological examination, plus semi-structured tests and interviews covering cognitive abilities, daily activities, depression, cerebrovascular disease, and Parkinson's disease. Dementia was diagnosed by consensus among the physicians according to the DSM-III-R criteria. Among the 455 participants, 16 cases of dementia were identified, including 13 with probable Alzheimer's disease and 1 each with vascular dementia, Parkinson's disease, and alcoholism. The rates of dementia were 0, 3·9 and 11·5% for the age groups of 50–69, 70–79 and 80–92; and 4·4, 2·0 and 0% for the education groups of 0–1, 2–6 and 7–15 years of schooling. No sex difference was found after controlling for education. The Chinese version of the CASI had an intraclass retest reliability of 0·90. Using a cut-off score of ≤ 50 for dementia, the sensitivity was 0·88 and the specificity was 0·94. The preliminary study suggests that the CASI can be used in Chinese populations with generally low education levels and that Alzheimer's disease was the most common type of dementia in this population.