This paper reports the results of an exploratory analysis among patients in the Endophthalmitis Vitrectomy Study to determine if there was a different response to treatment in diabetes and whether the signs and symptoms of endophthalmitis differ between diabetic and nondiabetic patients. Patients in this multicenter clinical trial were followed for 9 months after random assignment to either vitrectomy or tap/biopsy. Outcome measures included visual acuity assessed in standardized fashion. Fifty-eight of 420 study patients were diabetic. Diabetics presented with slightly worse vision and ocular media. Only 39% of diabetics compared with 55% of nondiabetics achieved 20/40 final vision. Both diabetic and nondiabetic patients who presented with vision of only light perception (LP) had better visual results with immediate vitrectomy. For those who presented with better than LP vision, diabetics achieved 20/40 more often with vitrectomy (57%) than with tap/biopsy (40%), but non diabetics did equally well with vitrectomy or tap/biopsy. In the diabetic group, small numbers did not allow adequate statistical power to test treatment difference. A new clinical trial is needed to determine if in fact there is a difference in response to treatment among diabetic and nondiabetic patients who present with better than LP vision.