The aim of this study was to demonstrate the effects of vitamin D treatment on ultrastructural changes and AMHR2 expression in the ovary in PCOS rat model. A total of 24 female prepubertal rats were divided into 3 groups. In group 1, sesame oil was injected and used as control group. In group 2, PCOS was created by the injection of 6 mg/kg/day DHEA. In group 3, PCOS was created and 120 ng/100 g 1,25 (OH)(2)D3 treatment was performed. At the end of the 28th day, the blood samples were collected. The ovarian tissues were obtained for electron microscopic and immunohistochemical examinations.