Partial hepatectomy produced a 4-5 fold increase in the O^6-mG-DNA methyltransferase activity of rat liver homogenate. to catalyze the removal of methyl group in O^6-methylguanine from DNA. This enzyme activity was maximal at 48 h after partial hepatectomy. When the 3H-methylated enzymes of the normal liver and partially hepatectomized liver were compared on DEAF-cellulose (Whatman DE-52) chromatogram, there was no difference in the elution pattern of enzymes but difference in the protein profile. Both the methylated enzymes were eluted at 0.17 M NaCl.