In order to clarify the involvement of oxidative stress inin vitrosugar-induced cataractogenesis, we examined changes in lipid peroxide, reduced glutathione, vitamin E, and water contents following cataractogenesis in rat lenses cultured with 20 mM D-xylose over a period of 24 h. In D-xylose-treated lenses, an apparent opacity appeared at the equator after 6 h of D-xylose treatment, increases in lipid peroxide and water contents and decreases in reduced glutathione and vitamin E contents occurred with the appearance of opacity. We further examined the effect of the treatment of vitamin E in a liposomal form on cataractogenesis and the changes of lipid peroxide, reduced glutathione, vitamin E, water, and xylitol contents in rat lenses cultured with 20 mM D-xylose for 24 h. This vitamin E treatment significantly prevented not only cataractogenesis, but also an increase in lipid peroxide content and a decrease in vitamin E content in the D-xylose-treated lenses. However, the vitamin E treatment had no effect not only on a decrease in reduced glutathione content, but also on increases in water and xylitol contents, which are known to be induced via aldose reductase, in the D-xylose-treated lenses. These results indicate that not only osmotic stress but also oxidative stress should be involved in cataractogenesis in rat lenses cultured with D-xylose and support the involvement of oxidative stress inin vitrosugar-induced cataractogenesis.