An ultrastructural study of Bruch's membrane in 68 human eyes including at least five individuals from each of ten decades of life showed that changes began in the second decade in macular specimens but were delayed in nonmacular specimens. All specimens from 20-year-old donors had altered macular Bruch's membranes. The severity of changes increased with age. The most common change for all ages was debris on both sides of the elastic layer. Drusen sites often showed no debris in the underlying outer collagenous zone, suggesting that drusen may result from failure of dispersal of the accumulated material at these sites. Secretion by pigment epithelium of a "linear basal deposit" is a late (after the age of 50 years) change.