To quantify changes in choriocapillary density and in thickness of Bruch's membrane, the choriocapillaris, and the choroid in 95 unpaired, histologically normal human maculae aged 6 to 100 years and in 25 maculae with advanced age-related macular degeneration. Light microscopic, computer-aided, morphometric quantitative analysis. In ten decades, Bruch's membrane thickness increased by 135%, from 2.0 to 4.7 microns; the choriocapillary density decreased by 45%; the diameter of the choriocapillaris decreased by 34%, from 9.8 to 6.5 microns; and the choroidal thickness decreased by 57%, from 193.5 to 84 microns in normal maculae. In maculae with basal laminar deposit, geographic atrophy, or disciform scarring, the density of the choriocapillaris was 63%, 54%, and 43% of normal and the choriocapillary diameter was 81%, 73%, and 75% of normal, respectively. Choroidal thickness remained unchanged. Thickness of Bruch's membrane was only related to age (rs= 0.63) and not to age-related atrophy of the choriocapillaris. Age was also the strongest factor related to choriocapillary density (rs=-0.58). In advanced stages of age-related macular degeneration, the decrease in choriocapillary density and diameter was significantly larger than in normal maculae, but the thickness of the choroid and Bruch's membrane was the same. The latter was significantly thinner (81% of normal) in disciform scarring.