Marfan's syndrome (MS) is an inherited disease of connective tissue. The most characteristic ocular change is dislocation of lens, but myopia and retinal detachment also can occur. We examined 11 MS patients using electroretinography (ERG). 6 cases showed normal ERG. 5 cases had abnormal ERG. One had retinal detachment. 3 had myopia and 1 case suffered from secondary glaucoma. The defects of visual function were shown by electrophysiological test in those MS patients.