Five groups (controls, patients with possible, probable and definite multiple sclerosis (MS) and patients with neurological diseases other than multiple sclerosis) were tested by pattern evoked potentials. Four occipital areas were compared as to the latency of the first major positive component and the latency difference when stimulating the right and the left eye. An 8% increase of pathological findings was achieved by taking four instead of one response alone into account. Latency and/or latency difference was found to be abnormal in 91% of patients with definite MS and 95% of patients with definite retrobulbar neuritis in history. Position and number of electrodes in the occipital area proved to be of considerable significance. Asymmetries of the potential field are more easily detected and may enhance diagnostic efficiency.