Currently there is growing evidence on possible influence of vitamin D (VD) on reproductive function in both females and males. The relationship between VD and clinical or laboratory manifestations of polycystic ovary syndrome (PCOS) seems to be mostly evaluated. Patients with PCOS have been demonstrated to have significantly lower levels of serum VD and they also have the higher prevalence of vitamin D deficiency as compared to controls. Some studies documented the relation of VD to serum androgen levels, other found that VD correlated with metabolic parameters (body weight, insulin resistance and lipid profile) only. Several interventional studies demonstrated that VD replacement improved these metabolic parameters in PCOS women with VD deficiency. On the other hand some studies also documented improvement of ovarian function and androgen levels. Also vitamin D replacement may represent an additional treatment in VD deficient PCOS women with the aim to improve phenotypic manifestations. It requires further randomized interventional studies on larger groups of patients.Key words: metabolic syndrome - polycystic ovary syndrome - vitamin D.