Retinal periphlebitis appeared as an early sign of bacterial endophthalmitis in three patients, a 36-year-old man with bilateral Terson's syndrome who underwent vitrectomy for dense vitreous hemorrhage, a 78-year-old woman who had had intracapsular cataract extraction and penetrating keratoplasty after repair of a wound leak and pars plana anterior membranectomy, and an 18-year-old man who suffered an accidental penetrating ocular injury. Staphylococcus organisms were recovered from vitreous samples in all three cases. Although recovery of useful vision is rare after postvitrectomy endophthalmitis, the first patient attained a final visual acuity of 20/50. The visual acuities of the second and third patients returned to 20/25 and 20/20 respectively. In an experimental primate (cynomolgus monkey) model of bacterial endophthalmitis, retinal periphlebitis developed early and closely resembled the clinical findings in humans. Histopathologic studies confirmed the presence of inflammatory cells that infiltrated the retinal venules.