After injection of 3H dihydrotestosterone, concentration and retention of radioactivity occur in nuclei of certain neurons in the spinal cord and spinal ganglia as well as in dorsal and ventral root cells of chick embryos at day 10, 12, and 18. Cell of the glycogen body show nuclear labeling at day 12, but not at day 18. In motor neurons in the midlumbar and midbrachial regions in lamina IX and in single neurons in laminae I/II, the nuclear retention of androgen is strongest, but relatively weak in ventral horn cells in thoracic and sacral segments. Neurons with nuclear labeling are also found scattered in other laminae of the dorsal and ventral horns as well as in the lateral column. When unlabeled dihydrotestosterone is administered before 3H dihydrotestosterone, nuclear uptake of radioactivity is prevented, which is not the case, when estradiol is used. The results from these autoradiographic studies indicate the presence of nuclear receptors and suggest androgen effects during prenatal stages of development.