Ophthalmic examination of 64 307 Aborigines and 41 254 non-Aborigines in remote rural Australia during the course of the National Trachoma and Eye Health Program revealed a positive correlation between the prevalence of senile cataract and levels of climatic ultraviolet (UV) radiation. Aborigines were more likely to be affected by senile cataract than non-Aborigines. It seems that Aborigines who live in areas of higher UV irradiation are more likely to acquire cataract; more likely to acquire the condition earlier in life; and more likely to be blind or visually disabled by it, than their counterparts living in areas of low UV irradiation. Provision of adequate shelter in areas of high insolation, where most cases of cataract occur, is likely to be an effective preventive measure.