Four cases of acute retinal necrosis (ARN) syndrome were studied virologically. Varicella-zoster virus (VZV) antigen was demonstrated by immunofluorescence in cells from vitreous aspirates of two cases. No herpes simplex virus (HSV) or cytomegalovirus (CMV) antigens were detected by the same technique. Antibody to VZV in vitreous fluid was present in two cases; however, it was not detected in sera. Although virus isolation was unsuccessful, these findings strongly suggest that VZV may play an important role in the etiology of ARN syndrome.