PURPOSE: To describe cases of postoperative endophthalmitis in the European Society of Cataract & Refractive Surgeons (ESCRS) study of the prophylaxis of endophthalmitis, compare characteristics of unproven cases and cases proven by culture or polymerase chain reaction, and compare the characteristics with those in other reported series. SETTING: Twenty-four ophthalmology units in Austria, Belgium, Germany, Italy, Poland, Portugal, Spain, Turkey, and the United Kingdom. METHODS: Univariable and multivariable logistic regression models were used to analyze data for statistical association of signs and symptoms in cases with proven or unproven endophthalmitis. Specific data describing characteristics of the cases were compared between the 2 types of cases. RESULTS: Data from 29 endophthalmitis cases were analyzed. Swollen lids and pain were statistically associated with proven cases of endophthalmitis on univariable regression analysis. Multivariable analysis indicated that swollen lids and an opaque vitreous were associated with proven cases. Five cases of endophthalmitis occurred in the cefuroxime-treated groups. No case of streptococcal infection occurred in the cefuroxime-treated groups. However, cases of infection due to streptococci showed striking differences in visual acuity and were associated with earlier onset. Characteristics in the 29 cases parallel results in previous studies, such as the Endophthalmitis Vitrectomy Study, although the addition of a control group in the ESCRS study elicited additional findings. CONCLUSION: Swollen lids, pain, and an opaque vitreous were statistically associated with proven endophthalmitis cases in the ESCRS study.