1. The dominant structures of ependyma of cerebral aqueduct in the rabbit are the cilia, microvilli, spherical structures and three types of the supraependymal cells that were observed with SEM and TEM.

2. Cases of cerebral aqueduct cyst, gigantic cyst arising from the diploe of cranial bones with intracranial extension, and intradural spinal hydatid cysts have been reported.

3. Along the cerebral aqueduct there were longitudinal parallel cristae, which was lined by simple cuboidal or columnar epithelium.

4. The main trend of medial part of NAcp was to the stria terminalis, thalamus, the place around cerebral aqueduct, and ventral midbrain.

5. Results:The NOS positive CSF contacting neurons were mainly at the cerebral aqueduct and the third ventricle(3V).

6. The ultrastructural characteristics and their functions of ependymal epithelium of the cerebral aqueduct in rats were studied by transmission and scanning electron microscopy.