In 97 embryos and fetuses (6--40-week-old) quantitative analysis of the ovarian growth, dynamic of development of sex cell population and their mitotic activity have been morphologically studied during prenatal development. It has been demonstrated that sex differentiation of the ovaries takes place at the beginning of the 6th week. Connective tissue cords of the cortical substance stroma have been stated to appear in 6-week-old embryos, develop centrifugally and reach covering epithelium by the 19th--20th week of embryogenesis. Connective tissue elements of the ovarian tunica albuginea appear on the 27th week and by the 40th week the ovarian tunica albuginea is distinctly seen. Formation of the medulary substance germ beginning on the 6th--7th week has been observed when the gonade is separated from mesonephros and mesovarium is formed. Maximal mitotic activity in the oogonium occurs on the 11th -- 26th weeks. During the same period (the 11th -- 17th weeks) the relative amount of germ cells reaches its maximum, and most of oocytes achieve the meiotic prophase. After the 17th week of the intrauterine development, an intensive proliferation of the ovarian somatic elements and folliculogenesis are observed.