To determine the possible electrophysiologic changes in migraineurs with or without visual aura, we investigatedpattern-reversal visual evoked potentials in 39 patients. We compared the mean P100 latency and amplitude of 16patients with aura, 23 patients without aura, and 17 age- and sex-matched normal subjects. There were no significantdifferences between groups. There was no correlation between age and the parameters in any group. However, in 7 of23 patients without aura, the P100 latency was longer than the mean control value + 2 SD. The mean disease duration inthis subgroup was significantly longer than the means of the remaining 16 patients without aura or the patients with aura(P<0.05 for each). This suggests the possibility that P100 latency prolongation is a consequence, but not an entitycaused by the pathogenetic mechanism of the disease from the beginning.