Male infertility is far easier to investigate than female, so the male is often checked first by being asked to provide a fresh sample of ejaculated semen for analysis in a laboratory. If this shows that the sperm are alive and healthy and the joint factors above are absent, then investigation of the woman can commence. An abnormal sample of semen will result in extensive detailed investigations to determine the cause of the abnormality.
If a man is impotent (unable to sustain an erect penis) then obviously successful intercourse is not possible.
Other causes of infertility due to the male include the regular wearing of tight clothing while exercising (eg. bike pants) that keeps the testes against the warm flesh in the groin and overheat them, premature ejaculation results in the man ejaculating semen before penetration of the vagina, surgery to the prostate gland may cause impotence or retrograde ejaculation, damage or infection to the testes that results in reduced sperm production (eg. torsion of both testes, undescended testes, failure of the testes to develop normally, bacterial or viral infections of the testes), infection of the testes during mumps, tumours or cancer of the testes, and irradiation or direct injury of the testes.
Genetic diseases such as Klinefelter syndrome will result in poorly functioning testes.
When he enters a new relationship, it is not unknown for a man to deliberately forget, or subconsciously repress the memory, that he has previously had a vasectomy, and the discovery of this during a physical examination may prove embarrassing to both parties.