We report the effects that sectioning the superior ovarian nerve of infantile female rats has on their follicular development at different ages before puberty. Compared with the control group, sham-operated animals showed a significant decrease in the number of measured follicles in right and left ovaries, although no difference in the follicular atresia ratio was observed. Animals with a sectioned left superior ovarian nerve (SON), killed 12 days after surgery had a significant increase in the number of follicles in the ovaries. Most of the follicles were atretic. Sectioning the right SON induced contrasting effects in the ovaries of animals killed 4 and 16 days after surgery. Rats with a denervated (right) ovary showed a decrease in the number of follicles and a greater number of atretic follicles compared with the control group, whereas the innervated (left) ovary showed an increase in measured follicles compared with the control group. Bilateral sectioning had no apparent effect on the total number of follicles measured, although an increased number of atretic follicles in both ovaries was observed. Animals with a unilateral section of the SON, killed 8 and 12 days after surgery, showed a decrease in serum concentrations of estradiol. In turn, animals killed 16 days after surgery showed a significant increase in estradiol and a decrease in the progesterone serum concentration. These results suggest that sympathetic innervation of the ovary via the SON has a stimulatory role in the regulation and differentiation of follicular growth.