Apoptosis has been largely analyzed in the testis. Nevertheless, the epididymis has been scarcely studied. We analyzed the number of apoptotic cells in the different regions (caput, corpus and cauda) of the epididymis of the South American rodent Octodon degus both young and senile. Apoptosis was identified using the TUNEL method which detects in situ DNA fragmentation. Apoptosis was detected in the principal cells of the epididymal epithelium. The caput epididymis was the region more affected. The caput of young animals showed that 0.32/1000 cells were apoptotic in contrast to 5.1/1000 of senile animals. Also in the cauda epididymis apoptosis is increased with age, appearing 0.14/1000 and 3.9/1000 in young and senile animals, respectively. On the other hand, we used a immunocytochemical method to localize the stress protein HSP70. HSP70 appeared notably increased in the principal cells of the cauda epididymis of senile animals. Changes in the epididymal epithelium are probably due to the low androgen levels existing in senile animals and are a region dependent phenomenon