This study aimed to estimate the number of Australians over 50 with cataract in the years 2001 and 2021. Data from two population-based studies were pooled: the Blue Mountains Eye Study and Melbourne Visual Impairment Project and Australian Bureau of Statistics population projections were used. Similar definitions for the three cataract types were used in the two studies (nuclear ≥ grade 4, posterior subcapsular ≥ 1 mm, cortical ≥ 10% lens area or ≥ 25% circumference). Combining the three types and prior surgery, it was estimated that in 2001, 1.7 million Australians had clinically significant cataract in either eye and 320 000 had previously undergone cataract surgery. It was estimated that the number of persons with cataract will rise to 2.7 million by 2021 (over 500 000 will have had cataract surgery). The number of Australians with cataract will grow by two-thirds during the next 20 years, reflecting continued population ageing. Health care delivery systems will need to develop methods to handle this increased workload.