Parapapillary chorioretinal atrophy is a morphological feature of glaucomatous optic nerve damage since it occurs more often and is larger in glaucomatous eyes than in normal eyes. This study was undertaken to find the histological correlation. Optic disc photographs and histological sections through the optic disc of 21 human eyes enucleated because of malignant uveal melanoma were morphometrically evaluated. Seventeen eyes had normal intraocular pressure and four eyes showed elevated intraocular pressure and glaucomatous optic disc cupping. Ophthalmoscopically, the parapillary chorioretinal atrophy was divided into zone 'alpha', located peripherally and characterised by irregular hypopigmentation and hyperpigmentation, and zone 'beta' located close to the optic disc border and showing visible sclera and visible large choroidal vessels. Histologically, zones 'A' and 'B' were differentiated. Zone 'A' peripheral to zone 'B' showed irregularities in the retinal pigment epithelium. It consisted of an unequal distribution of melanin granules and partial atrophy of cells. In zone 'B' adjacent to the optic disc, Bruch's membrane was bared of retinal pigment epithelium cells and the photoreceptors were markedly reduced in density or were completely missing. In a direct clinical histological comparison, zone 'A' correlated significantly with zone 'alpha' (r = 0.66; p < 0.01), and zone 'B' correlated with zone 'beta' (r = 0.99; p < 0.0001). Zone 'A', 'B', 'alpha' and 'beta' were larger in the four glaucomatous eyes than in the normal ones. The findings indicate that zone 'beta' represents histologically a complete loss of retinal pigment epithelium cells and an incomplete loss of adjacent photoreceptors. Zone 'alpha' may be the histological correlate of irregularities in the retinal pigment epithelium.