Objective  To study the effect of high glucose and tea polyphenols  (TPs) on the interaction of human mesangial cells and endothelial cells.  Methods  Mesangial cells and endothelial cells were cultured alone or  together in high  glucose media with or without TPs for 0-h, 12-h and 36-h respectively. The ex pressi ons of TGF-β  1-mRNA in the cells were measured by RT-PCR. Resul ts  High glucose i ncreased the expression of TGF-β  1-mRNA in co-cultured mesangial cells  as well as  in co-cultured endothelial cells and the effect became more prominent than in  sing le-cultured cells,which could be interruptted by TPs more effectively in co-cu ltured cells than in single-cultured  cells. Conclusions  (1)There is some kind of interaction betwee n human mesangia l cells and endothelial cells in high glucose condition, and the interaction can  increase the expression of TGF-β  1-mRNA. (2)TPs inhibit the expression  of TGF-β  1-mRNA by affecting the intercellular interaction between the  mesangial c ells and the endothelial cells.