Purpose: To investigate the spectrum of organisms causing endophthalmitis and their sensitivity to commonly used antimicrobial agents. Methods: Medical records of 80 consecutive patients treated at Beyoglu Eye Hospital for endophthalmitis from January 2001 to April 2006 were reviewed. Specimens were obtained from either the vitreous (93%, 81/87) or anterior chamber (7%, 6/87) during pars plana vitrectomy or vitreous tap, and were inoculated into blood culture bottles. A Kirby-Bauer disk diffusion test was performed to determine antibiotic susceptibility. The outcome measures included isolates identified and antibiotic sensitivity of the specimens. Results: Fifty-six of 87 (64.4%) isolates were Gram-positive organisms, 29 (33.3%) were Gram-negative organisms, and 2 (2.3%) were fungi. The most common organism group identified was coagulase-negative staphylococci in 26.4% (23/87). While vancomycin was active against all Gram-positive isolates tested (100%), ceftazidime had the highest susceptibility rate (100%) for Gram-negative organisms isolated. Conclusions: Although coagulase-negative micrococci predominated in this series, a high isolation rate for Gram-negative organisms was obtained. High susceptibility rates for ofloxacin make it an alternative to ceftazidime and vancomycin in both Gram-negative- and Gram-positive-derived endophthalmitis, respectively. Studies with larger series and additional antibiotics are needed to confirm these findings. Copyright (C) 2008 S. Karger AG, Basel.