Lead, a potent reproductive toxicant in humans and experimental animals, was used to detect the morphological basis of ovarian toxicity in mice by counting the various stages of follicular development using different doses of lead acetate (0, 2, 4 or 8 mg/kg/d) for 60 d (5 d/wk) by oral gavage. Our results revealed that while small and medium follicles were significantly affected even at the lowest dose (2 mg), the large follicles were affected mostly at the highest dose. Atresia even in the medium follicles reflected the extent of damage caused by lead. These findings correlated well with increased blood lead levels. Therefore, lead seems to affect the follicular development and maturation, if mice are exposed to sufficiently high concentrations of metal through the oral route.