Follicular development represents one of the essential functions of the ovary. It was done a lot of various classifications including kinetics or morphometry of growing follicles. All these experiments were carried on adult animals and so very little was known about developing follicles in youngs. In the view of this, we decided to investigate the postnatal development of rat ovary. Ovaries from rats between 14-84 days were examined; our own modification was used for classification of follicles, the number of each type of follicles and their diameter was counted, the number of granulosa cells in small growing follicles was noted and diameter of luteal cell and its elements in luteal body in which ovulation took place, were described.