Radial glia of the developing spinal cord were examined by Golgi, electron microscopic and immunohistochemical methods in 40 human embryos and fetuses of ovulation age 6-20 weeks. As in developing cerebrum and cerebellum, gliogenesis in the spinal cord occurs much earlier than traditionally believed. The presence of transitional forms suggests that subependymal glia originate from detached radial glia that divide and differentiate in their new location. Well-differentiated astroglia evolve from radial glia as fetal age advances.