Senile macular degeneration is a leading cause of visual loss in the United States, England, and probably many other industrialized countries. The clinical manifestations of this disease include: drusen, atrophy of the retinal pigment epithelium, serous detachment of the retinal pigment epithelium, subretinal neovascularization, and disciform scars. Standardized techniques for defining these manifestations of senile macular degeneration are necessary for epidemiologic study of this disease. Such standardization is facilitated by the use of fundus photographs. If a visual acuity deficit is included in the definition of senile macular degeneration, care must be taken to assure that senile macular degeneration is responsible for the decreased vision. The Framingham Eye Study provides the best senile macular degeneration prevalence data. The rapid increase in prevalence of senile macular degeneration after the fifth decade is demonstrated in this study and is consistent with other studies. In fact, increasing age has the strongest association with senile macular degeneration of any of the risk factors considered to date. Many other possible risk factors have been identified but further investigation is necessary to verify these associations.