The spermatozoa are often “misdiagnosed” as azoospermia. Mr. Wang has been married for one year, but his wife has not yet gotten pregnant, so he went to the local hospital for a routine semen examination and was diagnosed as azoospermia by the local doctor, so he came to our fertility center. The doctor asked Mr. Wang to check his semen by centrifugation to look for sperm, and found that after centrifuging the semen, a small amount of motile sperm could be observed in the centrifugal sediment. The doctor told Mr. Wang that his diagnosis was not azoospermia, but cryptospermia, and that he could use these sperm for IVF to obtain a child. Mr. and Mrs. Wang were overjoyed and felt a sense of survival. According to the World Health Organization (WHO), cryptospermia is defined as the absence of spermatozoa in the fresh semen preparation slide, but after centrifuging the semen, spermatozoa can be observed in the centrifugal sediment. In contrast, azoospermia is defined as the absence of spermatozoa on microscopic examination after 3 or more semen centrifugations. Therefore, occult spermatozoa is similar to very severe oligospermia, but often presents as a condition between azoospermia and oligospermia in which sperm can sometimes be found in the semen or sometimes not. For occult spermatozoa, ordinary routine semen tests such as semen smear count or computer-assisted sperm analysis (CASA) are difficult to find sperm, and multiple rigorous semen centrifugation to find sperm is required before sperm can be detected. However, most hospital laboratories do not perform rigorous semen centrifugation for sperm, so cryptospermia is often “misdiagnosed” as azoospermia. What causes cryptospermia? Cryptospermia, similar to non-obstructive azoospermia, is a manifestation of poor testicular spermatogenesis. Sometimes it can be shipped out of the factory (sperm in the semen centrifugal sediment) and sometimes it is destroyed by aging before it can be shipped out of the factory (no sperm found in the semen). The causes of cryptospermia include karyotypic abnormalities or genetic deletions (Klinefelter’s syndrome, Y chromosome microdeletion), endocrine abnormalities (hypogonadotropic hypogonadism, Kallmann’s syndrome), poor testicular descent (cryptorchidism), inflammatory diseases of the reproductive system ( orchitis, epididymitis, seminal vesiculitis), mumps, severe varicocele, post-radiotherapy for tumors, taking drugs that inhibit spermatogenesis, poor lifestyle habits (long-term night work and staying up late, smoking, alcoholism, drug abuse) and harmful working environment (high temperature, high radiation, exposure to toxic chemicals), etc. A proportion of patients with azoospermia can be transformed into cryptospermia after treatment. The vast majority of patients, need to resort to IVF. First of all, several rigorous semen centrifugation for sperm examination, history and physical examination by a male physician, examination of seminal plasma biochemistry, sex hormones, karyotype and related genes are performed. Invasive operations such as testicular biopsy or epididymal puncture are generally not recommended to avoid causing decreased spermatogenic function of the testes or obstruction of the vas deferens. Then, spermopoietic medication and treatment for the cause of the disease are performed, and the above-mentioned bad habits and harmful working environment are abstained. However, only a very small number of patients can be converted to oligospermia or sperm count returns to normal after treatment and can conceive naturally or undergo artificial insemination. The vast majority of patients with occult spermatozoa require the use of IVF techniques to obtain fertility. When the spermatogenic function has improved and stabilized after treatment, as evidenced by the ability to find motile sperm in the semen centrifugal sediment for more than 2 consecutive times, then they are ready for second generation IVF (intracytoplasmic single sperm injection, ICSI). The couple should undergo genetic counseling, and a portion of patients with karyotypic or genetic abnormalities should undergo third generation IVF (preimplantation genetic diagnosis, PGD). Before the female partner’s egg retrieval, the male partner should preferably cryopreserve the sperm 1 to 2 times for backup. On the day of the female partner’s egg retrieval, the male partner will masturbate to retrieve sperm and try to use fresh sperm for intracytoplasmic single sperm injection. If no sperm can be found in the fresh semen or if there is too little fresh sperm to be used, the frozen sperm can be thawed and used. If suitable sperm is still not found, testicular sperm retrieval can be performed or the eggs can be frozen for backup.