AIM: To report an increased incidence of sterile endophthalmitis following intravitreal injection of preserved triamcinolone acetonide (IVTA) from 1 May to 31 July 2006. METHODS: Charts were reviewed for all patients who underwent IVTA injections between 1 January 2005 and 31 July 2006 at the offices of a referral vitreo-retinal practice. Patients were included if they presented post-IVTA with a clinical picture consistent with endophthalmitis. RESULTS: Between 1 January 2005 and 31 July 2006, 554 eyes underwent IVTA. Eleven eyes (1.9%) developed an endophthalmitis. All eleven eyes underwent vitreous tap and intravitreal injection of antibiotics. All cultures and gram stains were negative for bacterial or fungal organisms. From 1 May to 31 July 2006, 97 eyes underwent IVTA. Nine eyes (9.3%) developed sterile endophthalmitis. This represented a statistically significant (p<0.0001) clustering of cases. Triamcinolone acetonide phials from affected lot numbers were analysed and were all found to be negative for bacterial endotoxin (<0.05 EU/ml). CONCLUSION: Over the 19-month period analysed, 11 cases of sterile endophthalmitis occurred following IVTA, and nine of these cases were clustered over a 3-month period. No endotoxin was detected in the phials tested. The aetiology of this increased incidence of sterile endophthalmitis is still unclear.