The oxidative metabolism of the epididymis has been investigated in 40-day-old rats under normal and experimental conditions. No difference in the oxidative metabolism was observed between the initial, middle and terminal segments of the epididymal duct of normal rats. After bilateral or unilateral castration or efferent duct ligation, the oxidative metabolism was found to be exclusively dependent upon plasmatic androgens in the terminal segment in contrast to the proximal segment oxidative metabolism which is dependent of both normal luminal secretions and normal plasmatic androgens.