In order to reveal (1) the behavior of the tritium-labeled hydroxyl group (i.e., OT group) and (2) the effect of temperature on the dissociation equilibrium of tritiated water, the OT-for-OH exchange reaction in a homogeneous system was observed (1) using ion-exchange resins and HTO water, and (2) using hydrogen oxides and HTO water. Consequently, the following four conclusions were obtained: (1) The OT-for-OH exchange reaction occurred between each anion-exchange resin (or each metal hydroxide) and HTO water. (2) The higher the temperature is, the smaller the activity of both anion-exchange resin and metal hydroxide will be, and the activity of cation-exchange resin is large when the temperature is high. (3) The larger the degree of crosslinking in each Biorad AG1 resin is, the lower the activity of the resin will be. (4) The exchange rate for the OT-for-OH exchange reaction is small when the electronegativity of the metal ion in the metal hydroxide is large.