In mammals, most of the follicles can not be ovulated, and instead, are degenerated throughout the entire reproductive period. However, the precise mechanism of follicle atresia is unknown. Three weeks old female mice (ICR strain) were ${gamma}$-irradiated with a dose of LD$^{50}$ . Before irradiation (day 0) and at day 1, 2, and 3 after irradiation, the normal and atretic preantral and antral follicles of the left ovaries were morphologically observed. Atretic follicles at 2 days after irradiation had numerous cell debris, apoptotic cells and bodies, and polymorphonuclear leukocytes in the antral cavity. In severely atretic follicles, numerous polymorphonuclear leukocytes infiltrated into the follicle. The frequencies of atretic antral (58.0 $pm$8.6) and preantral follicles (27.3$pm$11.2) induced by ${gamma}$-radiation increased to 94.0$pm$3.4 and 86.9$pm$7.6, respectively at 2 days after irradiation (p<0.05). The number of follicles with one or more neutrophils in the largest cross sections at 2 and 3 days after irradiation significantly increased (p<0.05). It can be concluded that ${gamma}$-radiation triggers the recruitment of neutrophils into the follicles during degeneration. The ovarian follicles can make a role of informative biological end-point useful for disaster-prevention.