A scanning microdensitometric technique has been developed for measuring the optical density of black and white photographs of the optic disc. From the frequency distribution curve of all the densities of the whole area of the optic disc, a separate peak was identified as corresponding to the area of pallor of the optic disc. Areas of pallor were measured as percentage of areas of the total disc for normal, ocular hypertensive, open-angle glaucoma patients, and those with suspect discs. Median values of percent area of pallor showed correspondence with the clinical diagnosis, the glaucoma patients having significantly larger areas than the normal subjects. The microdensitometric technique provides an objective means of measuring the amount of optic dis pallor. It has potential usefulness for screening and for following up suspect and confirmed glaucomas to determine progression of the disease.