A 17-year-old white woman had an acute left maculopathy of unknown etiology. She was in excellent health and had only had rubeola at 3 years of age. Hruby lens examination of the left eye, visual acuity of 6/60 (20/200), revealed a normal vitreous, macular edema, intraretinal hemorrhage, and cotton-wool exudates. Xenon photo-coagulation was performed on the left eye. The visual acuity remained 6/60 (20/200) with drying of the retina. The patient remained in excellent health until 22 months after the initial ocular problem when she developed a left homonymous hemianopia. Then her mind deteriorated, and she became demented. We diagnosed subacute sclerosing panencephalitis after finding an increased spinal fluid gamma globulin, raised serum and spinal fluid titers of measles antibodies, and an electroencephalogram pathognomonic for this condition.