Infertility is defined as the inability to conceive after 12 months of regular, unprotected sexual intercourse. It affects around 8 to 12% couples worldwide. Depending on the cause, infertility is divided into female, male and idiopathic infertility. In 35% of cases the cause of infertility is determined by female factors, in 30% by male and in 20% of couples it is a combined cause. In 15% of cases, there is no clear cause of infertility, therefore defined as idiopathic infertility. The causes of female infertility are divided into ovulation disorders, uterine abnormalities, fallopian tube damage, peritoneal factors and other causes, and the causes of male infertility are divided into pretesticular, testicular, posttesticular and other causes. The investigation of infertility begins with simpler and less invasive diagnostic methods, and those more complex and invasive are left for later. The beginning of any successful diagnostic procedure lies in a well-taken medical history and a thorough physical examination. Further diagnostic procedures include hormonal and radiological treatment. Genetic testing may also be performed as well as some more invasive methods, like laparoscopy, hysteroscopy and testicular biopsy. Infertility treatment requires an approach as natural and less aggressive as possible and is based primarily on eliminating the cause. If the etiological treatment with a conservative and surgical approach is unsuccessful, assisted fertilization methods are used.