Humans are continuously exposed to harmful environmental factors, including Electromagnetic Fields (EMF) produced by home appliances, diagnostic tools and industrial instruments. The present study investigates morphologically the effects of EMF on ovarian follicles. Female Wistar rats were exposed to 3 mili Tesla EMF for 4 h day-1 for 4 months, the ovaries from both experimental and control groups were processed for Transmission Electron Microscopy (TEM) and TUNEL reaction technique. TEM revealed that in the oocytes from experimental group the nuclei were shrunken and zona pellucida appeared narrower than those in the control group. The number of microvilli were decreased significantly and in their cytoplasm there were several lipid droplets and organels were dispersed. Signs of apoptosis such as condensed nuclei, chromatin margination and nuclear membrane dilatation were common in granulosa and corona radiata cells from the EMF-exposed rats than those from the control group. Primary morphological changes in the granulosa cells from this group were retraction of granulosa cells, loss of microvilli and condensation or loss of mitochondrial cristae. The morphological changes in oocytes seem to indicate the cytotoxic effect of EMF and the changes occurred in granulosa cells coincide with initiation of apoptosis in granulosa cells. Present results suggest that EMF exposure may interfere with normal process of folliculogenesis.