Background. We aimed to examine both whether vitamin E prevented and whether it reversed the growth inhibitory effect of high glucose. Methods. For the preventive experiment, rat mesangial cells (RMC) were grown in control glucose medium with the addition of 100 M of vitamin E. High glucose (27.5 mM) was added to the medium concurrent with the vitamin E addition. The 3-(4,5-di-methylthiazol-2-yl)-2,5 diphenyltetrazolium bromide (MTT) assay was used to measure RMC proliferation. Our data confirmed the growth inhibitory effect of high glucose and showed that the growth inhibition was prevented by vitamin E. To examine whether vitamin E reversed the growth inhibitory effects of high glucose, RMC were grown in control and high glucose medium. Contrary to previous prevention type studies, vitamin E was not added to the medium until growth inhibition of the RMC by the high glucose was established. Results. Our data show that it took 5 days of vitamin E administration to reverse the growth inhibitory effect of high glucose. Conclusion. This is the first time that vitamin E has been shown to reverse this high-glucose-induced inhibition of RMC, suggesting that vitamin E reverses a potentially important pathogenetic process.