Microdeletions of azoosperm factor are one of the common genetic alterations in men with azoospermia and severe oligospermia. It is known that azoosperm factor microdeletions are mainly distributed in three overlapping regions on the long arm of the Y chromosome, proximal, middle and distal, called AZFa, AZFb and AZFc, respectively. Azoosperm factor has the following uses in clinical testing: First, the relationship between the loci of azoosperm factor microdeletions and semen type. For example, in people with reproductive dysfunction, patients are more likely to have azoospermia than severe oligospermia when there are deletions on AZFa and AZFb. Second, azoospermia factor microdeletion can manifest both as idiopathic infertility and as cryptorchidism. Cryptorchidism and testicular descent insufficiency are the most common male differentiation abnormalities, often associated with impaired spermatogenesis and a high prevalence of testicular cancer due to higher abdominal temperatures, while AZF microdeletion can cause an arrest of a certain stage of germ cell development and manifest itself in the form of some characteristic testicular lesion. As in the case of sexual inversion syndrome:46, the main clinical manifestations in XX men are testicular dysplasia, cryptorchidism, penis with hypospadias, and low or no spermatozoa. Third, the incidence of azoospermia factor microdeletion in patients with varicocele is similar to the incidence of idiopathic severe testicular lesions. Screening for AZF microdeletion in such patients can both aid in diagnosis and avoid unnecessary treatments such as surgery that attempt to increase sperm count in varicocele patients.