PURPOSE. Endophthalmitis remains a devastating complication of cataract surgery, despite improved methods of prophylaxis and surgical technique. The current study was conducted to identify sociodemographic, environmental, and clinical risk factors for the development of postoperative endophthalmitis, using population-based administrative data from Western Australia.METHODS. The Western Australian Data Linkage System identified all patients who underwent cataract surgery, along with those in whom postoperative endophthalmitis subsequently developed, from 1980 to 2000 inclusive. Cases of endophthalmitis were cross-referenced with other sources and validated by medical record review. After selection and preliminary analysis of potential risk factors, multivariate logistic regression modeling was used to estimate odds ratios for the selected variables.RESULTS. Over the 21 years, 210 cases of endophthalmitis occurred after 117,083 cataract procedures, yielding a cumulative incidence rate of 1.79 per 1000 procedures. The incidence of endophthalmitis decreased for extracapsular extraction over the whole period, but not for phacoemulsification over the recent 12 years. There was no risk-adjusted difference in the incidence rate of endophthalmitis for the various cataract surgery procedure types. However, a significantly higher risk was found in patients aged over 80 years, in having surgery in private hospitals, and to a lesser degree in having same-day surgery and surgery in winter. Cataract surgery with lacrimal or eyelid procedures dramatically increased the risk of endophthalmitis.CONCLUSIONS. It may be possible to reduce the incidence rate of postoperative endophthalmitis by almost 80% with a systematic approach to the management of elderly patients, hospital stay, and clinical protocols.