Hydrothermal reaction of dichloromethane (CH2Cl2) at I mol/dm(3) leads to the formation of glycolic acid without metal catalysts at temperatures of 200-250degreesC. The reaction consists of three steps. First CH2Cl2 is converted into methanediol through hydrolysis. The disproportionation of methanediol then produces methanol and formic acid. Finally, glycolic acid is formed from methanediol and formic acid catalyzed by the acid (HCl) generated by the dechlorination of CH2Cl2. The yield of glycolic acid exceeds 50% at 225 and 250degreesC.