Male fertility depends on a sufficient number of healthy, mature, functional sperm at the time of female ovulation. Every infertile couple should keep in mind that male and female reproductive systems have to work together to conceive. Minor dysfunctions on one side can be compensated by the other partner. This compensation no longer works with more severe dysfunctions in one partner and/or minor dysfunctions in both partners. For that reason, diagnostic tests for both sides are essential, i.e. both partners must be examined.