We tested platelet function in seven patients (four men and three women, ranging in age from 26 to 57 years) with bilateral acute retinal necrosis. Hyperaggregation was detected in six of the seven. Antiplatelet therapy (aspirin, 500 mg/day) together with corticosteroids or other drugs produced satisfactory results. Despite administration of antiplatelet drugs, two retinal detachments developed; both were surgically repaired. A lower dosage of antiplatelet agents in one case and late administration of it in another were thought to have caused the retinal detachments. After the acute stage was over or the retina was reattached, there were no further recurrences during a follow-up period of more than one year.