Autopsy samples from cerebral areas of five brains from patients with multiple sclerosis (MS) and from six control brains were stained with Perls acid ferrocyanide to detect nonheme iron present as hemosiderin. Positive iron reactions were observed only in MS sections surrounding demyelinated plaques. Myelinated white matter near the lesion contained numerous iron-laden ovoid bodied and axons that stained positively for iron. Positive reactions were also found within blood vessels of gray matter near the lesion. A possible source of the iron was extravasated blood.