The hydrodechlorination of CCl3-CF3 (CFC-113a) was studied over silica-supported metal catalysts. Pd/SiO2 and Pt/SiO2 catalysts showed high activity for the replacement reaction of the chlorine atoms in CFC-113a with hydrogen. On the other hand, Ru/SiO2 selectively catalyzed the dimerization and gave CF3-CCl=CCl-CF3 and CF3-CCl2-CCl2-CF3. CHCl2-CF3 (HCFC-123) and CCl2F-CF3, (CFC-114a) also dimerized into the corresponding C-4-dimers over the catalyst. The reactivity of CF3-having haloethanes on the Ru/SiO2 decreased in the order of CFC-113a much greater than HCFC-123 > CFC-114a much greater than HCFC-124. The selectivity of dimerization decreased with decreasing the reactivity of substrates.