In this study, eighteen Wistar female albino rats were used to observe the ultrastructural effects of toluene on the rat ovaries. The animals were divided into experimental and control groups. The experimental group was exposed to 3,000 ppm toluene/m(3) for 7 days and 8 h/day. At the end of the experiment the main ultrastructural findings related to the oocytes of the antral follicles of the experimental group were: abundant vacuoles, lytic areas, degenerative mitochondria in the ooplasm and blunt microvilli on the surface. Furthermore, the granulosa cells revealed prominent degenerative changes such as pyknotic nuclei, mitochondrial alterations and dilatation of the endoplasmic reticulum (ER) cisternae. It was interesting to note that the ultrastructure of primordial follicles was almost similar in both experimental and control groups. All these findings suggested that, although toluene did not affect the primordial follicles, the growing follicles showed degenerative changes attributable to the inhalation of a toxic agent such as toluene.