This study aims to investigate the effect of electromagnetic field (EMF) exposure which is environmental toxic agent on ovarian follicles. A total of 30 female Wistar albino rats are randomly divided into three groups (n=10) as Control, Sham, and EMF groups. The rats are not exposed any processes in Control group. The rats are kept in special cage for the same duration as in the EMF group without any EMF exposure in Sham group while the rats are exposed to 900 MHz EMF with a special mechanism in EMF group. At the end of day 28, the ovarian tissues are collected. Stereological and biochemical examinations are performed. Concerning the GSI values, there are statistical differences between the Control and EMF (p=0.001), and Sham and EMF (p=0.001) groups, respectively. There are also statistical differences between Control and EMF groups in terms of volumetric parameters including medullary, and follicular antral volumes. Regarding the biochemical parameters, there are statistically differences between the Control and EMF (p=0.000), and Sham and EMF (p=0.000) groups, respectively. It may be concluded that exposure to a 900-MHz EMF leads to changes in ovarian follicle volumes which may affect the ovarian reservoir.