Twenty-nine patients with severe visual loss in one eye from disciform macular dystrophy were prospectively studied for the incidence of visual loss in the fellow eye. Four developed such loss in the second eye during a mean period of follow-up of 32 months from the time of onset of visual loss in the first eye, an annual incidence rate of 5.2%. The degree of drusen and retinal pigment epithelial and subretinal pigment epithelial pathology correlated positively with the incidence of visual loss in the fellow eye.