We recorded pattern-reversal visual evoked potentials (P-VEP) from dissociated vertical deviation (DVD) patients to evaluate the sensory system abnormalities in DVD. 91 DVD patients with good visual acuity were studied. Normal subjects and horizontal strabismic patients without DVD were compared for evaluation. Transient and steady state P-VEPs were recorded from three EEG electrodes placed on the posterior scalp. Half-field checker-board reversal stimulation was applied to stimulate monocular temporal retina and responses from right and left hemispheres were also compared for evaluation. Paradoxical lateralization was observed in all normal subjects. Abnormal P-VEPs were observed in 4 of 20 (20%) horizontal strabismic patients without DVD when employing the transient stimulation method and in 2 of 8 (25%) when using steady state stimulation. Abnormal P-VEPs were observed in 31 of 67 (46.3%) DVD patients, with the transient stimulation method and in 20 of 25 (80.0%) DVD patients with the steady state stimulation method. The abnormalities were various and diverse. Our observations indicate that DVD patients frequently have an abnormal sensory system detected by P-VEP, and DVD might be a complex and multi-origin condition involving both sensory and motor systems.