Four patients with definite multiple sclerosis (MS) gave evidence of demyelinating plaques that produced a form of visual loss atypical of MS, i.e. homonymous quadrantanopsia (women, 22 and 30 years), and homonymous hemianopsia (men, 30 and 42 years). Cerebral magnetic resonance imaging (MRI) identified areas with increased signal intensity situated corresponding to the observed visual field defects. The results of visual evoked potentials (VEP) were in accordance with what should be expected from anatomical considerations.