Infertile male is defined as one who could not impregnate fertile female, after the coitus that has happened at the right time in oestrus. The causes of infertility can be classified as acquired and congenital. Acquired infertility has higher prevalence then congenital and it is caused by various inflammations, such as prostatitis and orchitis, trauma, hormonal imbalances, such as testicular degeneration and benign prostate hypertrophy. Certain drugs also cause permanent or temporary infertility and tumors. Congenital infertility is rare and it is caused by various genetic disorders, such as hermaphroditism or anatomy abnormalities like penile duplex. Diagnosis is made with combination of detailed clinical examinations, carefully taken anamnesis, history of patient diseases and macroscopic and microscopic sperm evaluation. It is hard to confirm the right diagnosis and it often stays unknown so prevention is the first step in reducing infertility. Detailed clinical examination, good breeding management, good blood lines and alternative methods like assisted reproduction tend to be the most succesful methods in reversing infertility problems.