Urayama et al. first reported acute retinal necrosis (ARN), a devastating, potentially blinding, necrotizing retinitis in 1971. The diagnosis of ARN is based on the clinical appearance and disease course. We know that herpes simplex virus (HSV) and varicella zoster virus (VZV) can actually cause a wide spectrum of clinical manifestations ranging from severe ARN to slow-progressing necrotizing and non-necrotizing types of inflammation, but proper initial treatment must be the most important matter for the management. The standard initial treatment for ARN may be intravenous acyclovir for 5 to 10 days, followed by oral acyclovir for 6 weeks. Additionally, treatment with a systemic corticosteroid and/or an antiplatelet agent is performed. Recently, prophylactic laser retinopexy or prophylactic vitrectomy before development of a retinal detachment has been reported to reduce the incidence of retinal detachment, which is predictive of the visual outcome in ARN. I will demonstrate the result of retrospective Japanese study concerning the effect of vitrectomy for the long-term visual outcome and discuss about the suitable initial treatments.