We conducted a retrospective, hospital-based study of patients who were diagnosed with bacterial endophthalmitis on admission to the Department of Ophthalmology, Hiroshima University Hospital, between January 1999 and December 2003. Thirty eyes of 30 patients were identified. Of these patients, 19 eyes had postoperative endophthalmitis, 8 eyes had penetrating trauma and 3 eyes were infected from an endogenous source. All of the patients underwent immediate three-port pars plana vitrectomy. Vitreous specimens of diabetic patients demonstrated a significantly higher incidence of positive bacterial culture. Diabetic vitreous appeared to be a good medium for culture. Visual acuity of hand motion or less at the latest follow-up visit was associated with the presence of diabetes. Prompt treatment with vitrectomy and intra-vitreal antibiotics is crucial for patients with bacterial endophthalmitis, especially if they are diabetic.