The secretion and localization of epididymal specific proteins ESP-1, ESP-2 were systematically studied by the PAGE-western blot and ABC immunocytochemical technique in the epididymis of the rabbit. The results indicated that ESP-1 and ESP-2 represented the rabbit epididymal specific proteins of 42 kd and 20 kd, respectively. They were immunoeytochemically negative in the testis, heart, liver, spleen, lung, kidney and skeletal muscle of the rabbit as well as testis and epididymis of the rat. However, in the rabbit epididymis, except the initial segment ESP-1 and ESP-2 were started to be positive from caput segment. The ESP-1 was displyed in the supranuclear area of the principle cells, while the ESP-2 was distributed evenly in the whole cytoplasm of it. Subsequently, the most heavy positive reaction was demonstrated in the corpus epididymis and the proximal segment of cauda. In contrast of the caput, the stereocilia of principle cells and lumen sperms of the cauda epididymis were positive also. However, in the distal segment of cauda the positive reaction in cytoplasm of principle cells was gradually decreased and became disappeared completely soon, while the stereocilia of it still remained heavy positive even in that of vas deferens. The epithelium of prostate gland and seminal vesicle were negative. These results indicated that both ESP-1 and ESP-2 were secretory proteins produced mainly in the principle cells of the corpus epididymis. After releasing into the lumen, they took part of epididymal fluid and might bind on the sperm to regulate sperm maturation. The possible physiological significance of ESP-1 and ESP-2 was discussed.