In recent years approximately 8% of the newborn Danes have been conceived by infertility treatment, and approximately half of the cases are due to male subfertility. Male infertility can be caused by several factors, and only in about half of the cases is it possible to disclose an aetiological explanation. It is important to elucidate possible reasons for male infertility as low semen quality might be a symptom of pituitary dysfunction, genetic disorders or testicular cancer.