Since delayed pattern evoked potentials (EPs) are a sensitive symptom of demyelination or compression of the optic nerve, a group of 33 patients with endocrine orbitopathy were examined in order to see whether or not, in this disease too, damage to the optic nerve could be detected at an early stage. Below a visual acuity of 0.4, all patients had delayed responses. Most interesting was the group of patients with normal visual acuity and delayed responses. Before conclusions can be drawn this group will have to be enlarged and followed up.