Infertility is the inability to conceive after at least one year of unprotected intercourse. Since most people are able to conceive within this time, physicians recommend that couples unable to do so be assessed for fertility problems. In men, hormone disorders, illness, reproductive anatomy trauma and obstruction, and sexual dysfunction can temporarily or permanently affect sperm and prevent conception. Some disorders become more difficult to treat the longer they persist without treatment.

Sperm development takes place in the ducts of the testes. Cell division produces mature sperm cells that contain one-half of a man's genetic code. Each spermatogenesis cycle consists of six stages and takes about 16 days to complete. Approximately five cycles are needed to produce one mature sperm. Energy-generating organelles inside each sperm power its tail so that it can swim to the female egg once inside the vagina. Sperm development is ultimately controlled by the endocrine system that comprises the hypothalamic-pituitary-gonadal axis.