Azoospermia is defined as the complete absence of spermatozoa upon examination of the semen [including capillary tube centrifugation (CTC), strictly confirmed by the absence of spermatozoa issued in urine after ejaculation]. The presence of rare spermatozoa (<500.000/ml) in seminal fluid after centrifugation is called "cryptozoospermia". The complete absence of spermatozoa should be confirmed with repeat testing after a long time, because many external factors (e.g., febrile episodes and some therapies) may cause transient azoospermia. Azoospermia is present in approximately 1% of all men, and in approximately 15% of infertile men. Azoospermia may result from a lack of spermatozoa production in the testes (secretory or Non-Obstructive Azoospermia, NOA), or from an inability of produced spermatozoa to reach the emitted semen (excretory or Obstructive Azoospermia, OA); however, in clinical practice both components are sometimes present in a single patient (mixed genesis azoospermia).The initial diagnosis of azoospermia is made when no spermatozoa can be detected on high-powered microscopic examination of centrifuged seminal fluid on at least two occasions. The World Health Organization (WHO) Laboratory Manual for the Examination of Human Semen and Semen-Cervical Mucus Interactions recommends that the seminal fluid be centrifuged for 15 minutes, preferably at a centrifugation speed of ≥3000 × g.