Electron microscopy of 15 human eyes from patients aged 2 to 82, was done to study aging changes in Bruch's membrane and their relation to senile macular degeneration. The membrane increased twofold to threefold in thickness from childhood to adult life. The basal laminas did not change. With increasing age the membrane accumulated 640 A and 1,100 A type collagen. Clumps were found near the choriocapillaris, often indenting its wall, and in the intercapillary zones. With increasing age vesicular structures accumulated in all zones, mainly internally. Tube-like structures, possibly altered collagen also appeared in the outer collagen zone. Because of these new accumulations the elastic layer became less distinct. Crystal formation was seen on collagen and elastic fibers.