Aging changes known to occur in Bruch's membrane may be associated with drusen formation and retinal pigment epithelial mottling, which often have a peripheral as well as a macular distribution. Few details of peripheral Bruch's membrane aging changes have been reported. We conducted a histochemical investigation of Bruch's membrane in 31 postmortem donor eyes and an ultrastructural morphometric investigation of these regional changes in a subgroup of 22 eyes. The age of our donors ranged from 12 days to 80 years. When we reacted 5 micron paraffin embedded sections of chorio-retinal complex fixed in 2% glutaraldehyde-1% paraformaldehyde, we observed increased PAS positivity, and staining with Weigert's elastin and alcian blue at pH 2.5 in Bruch's membranes from donors over 46 years. In this older group, the macula showed increased histochemical reactivity for glycoconjugates, glycosaminoglycans, collagen and elastin as compared with the equator and periphery. Thickening of Bruch's membrane was first detected in the periphery in tissue from donors aged 10 to 45. Thickening of macular Bruch's membrane was first detected in tissue from donors older than 45. The major proportion of thickening, which appears to be due to the deposition of fibrillar and amorphous material, occurred earlier in the inner than the outer collagenous zone. The equatorial region was relatively spared. Our findings confirm and extend the observations of the timing, regional predeliction, and extent of Bruch's membrane aging changes.