Using a differential display method, we identified sperm-associated antigen 6 (Spag6) as a gene with a dynamic expression profile within the chick embryonic spinal cord. The expression of Spag6 gradually decreased along with spinal cord development. Spag6 expression was detected adjacent to the ventricular zone of the spinal cord at embryonic day (E) 4. At E6, Spag6 was apparent in the ventral ventricular zone adjacent to floor plate and the surrounding region close to the ventricular zone, with additional weak expression at the adjacent region to the ventral horn. At E10, the Spag6 mRNA can be detected slightly in the ventral ventricular zone and surrounding region of dorsal ventricular zone. In the E6 hindbrain, Spag6 was detected in the roof, the ventricular zone adjacent to floor plate and the surrounding regions of the ventricular zones. In the E6 caudal diencephalon, Spag6 expression was detected adjacent to the ventricular zone. As Spag6 was expressed in areas containing ependymal progenitor cells and in the borders of undifferentiated regions, Spag6 may be involved in the development of ependymal cells and in the differentiation process of neuronal cells in chick neural organs.