Purpose: To evaluate the effect of N-acetylcysteine on selenite-induced cataract formation in a rat model. Materials and Methods: Thirty-four Sprague-Dawley rat pups were divided into three groups. Eight pups received only selenite on postpartum day 10 (group 1), 14 pups received selenite on day 10 and additional acetylcysteine on postnatal days 9 to 15 (group 2), and 12 pups received only saline (group 3, control). All pups were daily examined for the presence of cataract under the microscope, starting from the day their eyes opened. Glutathione and malondialdehyde levels were evaluated in both serum and lenticular samples while protein carbonyl level was studied only in lenticular samples. Results: In group 1, 50% of the rats developed dense nuclear opacities and 50% developed slight nuclear opacities, while in group 2 only 14.3% developed dense nuclear opacities and 21.4% developed slight nuclear opacities (p 0.05). None of the rats in group 3 developed any lens opacity. In lenticular samples, mean glutathione level was statistically lower in group 1 compared to groups 2 and 3 (p 0.05), while malondialdehyde and protein carbonyl levels were both statistically higher in group 1 compared to groups 2 and 3 (p 0.05). Serum level of glutathione was statistically lower in group 1 compared to groups 2 and 3 (p 0.05), while serum malondialdehyde level was statistically lower in group 3 compared to groups 1 and 2. Conclusions: N-acetylcysteine appears to inhibit selenite-induced cataractogenesis in the rat model, and this seems to be caused by the prevention of oxidative damage.