Although the frequency of cataract surgery has increased in the UK, the demand is still not being met. There is no evidence of whether Regional Health Authorities are meeting the national target of 150 cataract operations per 100,000 population. This paper describes variations in age-standardised rates of cataract surgery and lengths of hospital stay (LOS) between the 13 health districts in South West Thames Regional Health Authority (SWTRHA). A retrospective analysis of cataract surgery performed on South West Thames (SW Thames) residents during 1990 was undertaken using the Korner hospital activity data system. The residents of SW Thames Region had 6,729 cataract operations in 1990, producing an overall surgery rate of 266 per 100,000 resident population. Two-thirds of the operations were performed on women, and the greatest number of operations were in the 75-79 and 80-84 year age bands. Women aged over 75 had significantly higher age-specific surgery rates than their male counterparts. The mean age for women was 76.6 years and for men 71.9 years; 12% of cases had a length of stay less than a day (day cases) and 49% were discharged within two days. There were substantial variations in LOS between health districts. Age-adjusted rates revealed significant variations between districts, four of which had rates below the regional average. The crude cataract surgery rate for SW Thames residents has increased threefold since 1975. Women have a significantly higher rate of surgery, which may be due to social factors. Variations in LOS between districts cannot be explained by difference in age structure and may be caused by local custom and practice. It is possible for national, regional and district cataract rates to be calculated, and they are a useful indicator of how the need for cataract surgery is being met in the population.