Only when a patient presents a situation of azoospermia with normal hormonal assays the attention is focussed on the epididymis and in all other cases testicular damage is automatically suspected. However, there are many instances where oligospermia cannot be explained and where the testicular biopsy shows vigourous spermatogenesis. Detection of difficulties in epididymal transit is a new differential diagnosis of oligoasthenospermia. The delicate structure of the epididymis can be destroyed by infections that in extreme cases do cause complete obstructions but much more frequently lead to sub-total blocks. The diagnosis is made by comparing ejaculates with testicular biopsies and their very meticulous quantitative reading. A good selection of cases can lead to microsurgical repair of epididymal damage and significant improvement of sperm quality.