EVP [evoked visual potential] obtained by pattern reversal were recorded in 20 controls and 43 patients with established, probable or possible MS [multiple sclerosis] on the basis of MacAlpine''s criteria. While the latency of wave 1 of the EVP appeared stable in the controls (107.5 ms .+-. 7.46), lengthening of the latency of the EVP was seen in 77% of cases, confirming involvement of the visual pathways, though bulbar neuritis was known clinically in only 28% of patients. The value of this method of recording EVP for diagnosis of DS [disseminated sclerosis] was discussed.