From 1983 to 1992, 134 patients were treated for clinically suspected endophthalmitis. 61% of this endophthalmitis population consisted of cases that were referred to our clinic. In this nine year period antibiotic treatment was carried out according to three consecutively used guidelines. These three treatment schemes differed in antibiotic spectrum and mode of antibiotic delivery. In 68 patients we performed vitrectomy on account of clinical deterioration under antibiotic treatment. We did not find significant differences in visual outcome between the three treatment groups. The incidence of endophthalmitis following cataract or vitreous surgery did not change throughout the study period. There was however a dramatic decrease in incidence of post-traumatic endophthalmitis following the introduction of a prophylactic antibiotic treatment scheme consisting of fortified gentamicin and cefazolin eyedrops, and intravenously and subconjunctivally administered gentamicin, cefazolin, and clindamycin. In 55 of 68 cases in which vitrectomy was performed in conjunction with intravitreal antibiotics, a vitreous or anterior chamber specimen was cultured. 36 patients had a positive culture result. In the group with positive culture result 42% had better visual acuity in the post-treatment period than before treatment. In the group with a sterile culture result 79% had better vision after treatment.