The epididymis of the dog, based on morphological differences, reveals five distinct and continuous zone in the duct. It is observed zone I and zone II, both of them localized into the head. The third zone, or zone III, comprises the distal head and all the body. The fourth and fifth zones (zones IV and V), are restricted to the tail, localized into the proximal and distal Cauda epididymidis, respectively. Each zone can be readly distinguished on the basis of its own duct morphological characteristics. This distinction concerns mainly to the overall duct histology, and also to cytological appearence and epithelial lining constitution.