Contrast sensitivity and pattern visual evoked potential (VEP) were measured in cases of ocular hypertension and primary open-angle glaucoma at various stages. The visual field of each eye was examined quantitatively and the retinal nerve fiber layer and optic disc were precisely assessed with magnified stereoscope fundus photography. This study revealed that contrast sensitivity of the eyes with glaucoma was within the normal range in the very early stage of the disease. As optic nerve damage advanced, high- or low-frequency loss developed. Further optic nerve damage produced a level type of loss. Pattern VEPs also showed increasing abnormalities as glaucomatous optic nerve damage progressed. Measurements of contrast sensitivity and pattern VEP were found not to be as sensitive as quantified precise visual field measurement or color stereoscopic fundus photography for detection of minor optic nerve damage in cases of early glaucoma. These methods may be useful, however, as an objective and subjective monitor of progression of optic nerve damage in glaucoma.