Recent evidence indicates that glial cells have a wide range of funtions which are critical for maintaining a balanced homeostatic environment in the central nervous system(CNS) peripheral nervous system(PNS). Morever, astrocytes are known to participate in the tissue repair and neuroimmunologic events within the CNS through many kinds of growth factors and cytokines. We investigated the effect of TGF β<sub>1</sub>, on the growth and biochemical changes of rat glial cells in culture. The proliferative effect was determined by <sup>3</sup>H-thymidine uptake and the double immunostain with anti-cell-specific marker and anti-Bromodeoxyuridine(BrdU) antibody. To check the effect of biochemical changes we compared the amounts of glial fibrillar acidic protein(GFAP) and the activity of glutamine synthetase(GS) in astrocyte. And the amounts of myelin basic protein and the activity of 2 ,3 -cyclic nucleotide phosphohydrolase(CNPase) were measured in oligodendrocyte and the amounts of peripheral myelin in Schwann cell. When TGF β<sub>1</sub>, was treated for 2 days with cultured glial cell, TGF β<sub>1</sub>, decreased the <sup>3</sup>H-thymidine uptake and proliferation index of double immunostain of astrocytes, which indicates the inhibition of astroglial DNA synthesis, but stimulated the growth of Schwann cell. Also, TGF β<sub>1</sub>, decrease the GS activity and increased the amounts of GFAP in astrocyte. In the case of Schwann cells the amounts of peripheral myelin was increased when treated with TGF β<sub>1</sub>. However, TGF β<sub>1</sub>, didn t show any effect on the proliferation and biochemical changes in oligodendrocyte. These results suggest that TGF β<sub>1</sub>, might have a critical action in the regulation of proliferation and biochemical changes in glial cells, especially astrocyte.