Several types of the epithelial cells were classified by ultrastructural observation through transmission electron microscope in the rat epididymis. Ultrastructural studies showed that the principal cells, basal cells and narrow cells are located in all the regions of the epididymis and the light cells are present only in the corpus and cauda epididymis. It was observed that the columnar epithelial cells like the principal cells, light cells and narrow cells contain several secretory vesicles and there are halo cells migrating in the several regions. The basal cells showed the elliptical forms in the caput and corpus region and the global forms in the cauda region.