The acute retinal necrosis syndrome is manifested by diffuse uveitis, vitritis, retinal vasculitis, and acute necrotizing retinitis (see Part 1). We studied the histopathology and electron microscopic findings of an eye enucleated from a 67-year-old man with typical acute retinal necrosis. Histology showed profound acute necrosis of the retina, retinal arteritis, and eosinophilic intranuclear inclusions in retinal cells. Electron microscopy demonstrated a herpes group virus in all layers of affected retina. The implications of these findings for antiviral and other treatments are discussed.