The prenent study was designed to test the hypothesis that the inhibitory effect of elevated glucose levels on mesangial cell growth might be mediated by transforming growth factor β (TGF β). Increased glucose levels inhibited mesangial cell proliferation in a concentration dependent manner. The addition of a rabbit antipncine TGF β1 neutralizing antibody significantly enchanced the cell proliferation in both normal (5.5mM) and high (50mM) glucose media (12% and 30% respectively), and almost completely blocked the growth inhibition induced by high glucose media. TGF β assay demonstrated mesangial cells produced more active than latent TGF β after growth in high glucose media. We conclude that TGF β functions as an autocrine cytokine in mesangial cells growth and the production of TGF β is modulated by high glucose concentration. The growth inhibition induced by high glucose levels may be largely mediated by endogenous TGF β. The prenent study was designed to test the hypothesis that the inhibitory effect of elevated glucose levels on mesangial cell growth might be mediated by transforming growth factor β (TGF β). The addition of a rabbit antipncine TGF β1 neutralizing antibody significantly enchanced the cell proliferation in both normal (5.5 mM) and high (50 mM) glucose media (12% and 30% respectively), and almost completely blocked the growth inhibition induced by high glucose media. assay demonstrated mesangial cells produced more active than latent TGF β after growth in high glucose media. We conclude that TGF β functions as an autocrine cytokine in mesangial cells growth and the production of TGF β is modulated by high glucose concentration. The growth inhibition induced by high glucose levels may be substantially mediated by endogenous TGFβ.