The distribution and development of ferritin-containing cells were studied immunohistochemically in the cerebrum at ages ranging from human fetuses to adults. The predominant cell type labeled with antiserum to ferritin was the oligodendrocyte. In frontal and occipital lobes, positive cells appeared at 25 weeks gestation in subcortical and periventricular white matter, and increased earlier in the white matter than in the cortex. They also appeared at 25 weeks gestation and increased continuously in infancy in the putamen and globus pallidus, as well as in the frontal and occipital lobes. This development of ferritin-positive glia may be related to the process of myelination and maturation of oligodendrocyte.