To examine the association of some common medical conditions with functional limitation in elderly Chinese aged 70 years and over, to estimate the percentage of disability attributable to individual diseases, and to attempt to identify predisposing factors by documenting the development of functional limitation over an 18-month period in those subjects with a particular disease who were independent initially.The cross-sectional data set consisted of 2,032 (999 M, 1,033 F) subjects aged 70 years and over recruited by random sampling (stratified by age and sex) of all recipients of old-age and disability allowance, which covers over 90% of the elderly population. Information regarding medical condition and functional assessment of ten basic activities of daily living using the Barthel Index were obtained by personal interviews and physical assessment of the respondents at their places of residence. The longitudinal data set consisted of 1,334 subjects with no functional limitation at baseline who were alive after 18 months. Functional status was reassessed.After adjusting for age and sex, diseases associated with severe functional limitation (Barthel Index < 15) were dementia, stroke, Parkinson's disease, and fractures. Those associated with mild to moderate functional limitation (Barthel Index 15-19) were the same, with the addition of asthma and diabetes mellitus. The attributable fraction for severe limitation was highest for stroke, dementia, and fractures. Stroke and arthritis were identified as diseases predisposing to mild to moderate functional limitation over an 18-month period among those subjects who were independent initially.Stroke, dementia, and fractures were the main chronic diseases associated with severe functional limitation in elderly Hong Kong Chinese. Attempts to reduce the disability burden in this population should target these diseases.