The Hong Kong 1981 Census found a high prevalence of blindness in the age group aged 65 and above. Visual defects short of blindness are also a special problem among the elderly and cataract is one of the most important causes. We have studied the prevalence of cataract among 546 subjects living in homes or hostels for the aged in a New Town in Hong Kong. Cataract was defined as having a lens opacity and visual acuity worse than 20/100 in either eye. A prevalence of 45% among men and 32% among women was found. There was significant difference in prevalence between men and women aged below 75 but little sex difference was noted for the older age groups. Among the cataract cases detected on screening, about half had not had the diagnosis made previously. The results confirm the need for more epidemiological and health care studies on the visual problems among the aged.