Polycystic ovary syndrome (PCOS) is considered to be the most prevalent cause of anovulatory infetility. Despite years of extensive research, the exact pathophysiology of this syndrome remains unknown. Factors which could have a crucial role in the etiopathogenesis of PCOS, are periferal insulin resistance and at the same time ovarian hypersensitiviy on normal insulin serum level, ovarian hyperandrogenism, althered gonadotropine secretion and abnormalities at the adipose tissue level. The main focus of nowdays researche is based on altered secretion of AMH, and vitamin D defficinecy. Vitamin D plays a physiologic role in a reproduction both in men and women. It has an impact on progesterone production in human granulosa cells and ovarian follicular development, alters serum AMH levels and alters follicle-stimulating hormone sensitivity. Women with PCOS often have vitamin D deficiency defined by serum levels of 25(OH)D3 < 20 ng/mL with the prevalence of 67 to 85%. Low levels of vitamin D can lead to worsening of the symptoms in patients with PCOS, including insulin resistance, ovulatory dysfunction and irregular periods, infertility, hyperandrogenism, obesity, and also can increase the risk of cardiovascular diseases in these patients. Vitamin D supplementation could have a potentially important role in fertility in patients with PCOS because vitamin D appears to reduce insulin resistance and serum androgen levels. Furthermore, vitamin D is related to obesity, decreases serum levels of AMH, has an effect on serum levels of PTH and has an impact on molecules in oxidative stress reactions in the follicles. Further research is needed to determine the exact mechanism of action of vitamin D and to clarify the effect of vitamin D supplementation on fertility in patients with polycystic ovary syndrome.