It has been hypothesized that senile cataract may serve as a marker for generalised tissue aging, since structural changes occurring in the proteins of the lens during cataract formation are similar to those which occur elsewhere as part of the aging process. An earlier analysis we carried out to test this hypothesis revealed a strong age-dependent relationship between undergoing cataract surgery and subsequent mortality. Relative risks for dying over 9 yr of follow-up were particularly increased for individuals who had developed cataract requiring operation between the ages of 50-65. This finding prompted us to test the hypothesis that younger patients undergoing surgery for cataract (those in which surgery was undertaken at 50-65 yr of age) would tend disproportionately to be resident in areas of generally lower socioeconomic status. A population-based linked health data resource containing data on all hospital separations in the province of British Columbia was used to examine this hypothesis. Linkage to Canadian census data was used to assign a socioeconomic decile to the area of residence for all individuals in British Columbia who either did, or did not, undergo cataract surgery over a 3 yr period, and were aged 50-95. Relative to those who resided in the highest socioeconomic areas, odds ratios for undergoing cataract surgery between 50 and 65 yr of age were significantly greater than 1 for the four lowest socioeconomic deciles. This association was observed despite a conservative bias in our setting that favoured those of higher socioeconomic status tending to receive earlier treatment. The results of this ecologic study prompt consideration of whether factors which have the dual attributes of being correlates of socioeconomic status and implicated in the development of cataract may play a role in mediating the processes involved in the well known association of socioeconomic status and mortality.