Pre-existing dementia among patients with acute stroke is common, and adversely affects outcomes. Only a few studies have been published on prestroke dementia (PSD), none of which have investigated a consecutive stroke cohort in an Asian patient population. The objective of this study was to examine the prevalence and clinical correlates of PSD in Chinese stroke patients in Hong Kong. Close and reliable informants of 289 stroke patients who were consecutively admitted to the medical wards of a university-affiliated regional hospital completed the Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE) within 1 week after their relative's admission. The presence of PSD was defined as an average IQCODE score of >or= 4.00. In addition, a wide range of demographic and clinical variables were examined and recorded.Twenty-two participants (7.6%) had PSD. The frequency of PSD in the group of subjects (n = 73) who were assessed within 48 hours after their admission was 12.3%. Univariate analysis found that PSD was associated with age, marital status, atrial fibrillation (AF), previous transient ischaemic attack (TIA), leukoaraiosis, and cerebral atrophy index (CAI). Multivariate logistic regression suggested that CAI, age, AF, and past TIA were independent risk factors for PSD. The low prevalence of PSD in Chinese patients in comparison with their Caucasian counterparts may be due to the difference in the time frame of the assessment. Comparative studies involving both Caucasian and Chinese stroke patients are required to further explore the role of AF and TIA in the development of PSD in both Chinese and Caucasian patients.