The dissolving rate of sol-gel thorium oxide is increased three- to sixfold when approximately 1 wt% MgO is incorporated into the thoria. The MgO is introduced by adding an Mg(NO3)2 solution to the thoria sol. Thoria containing MgO is suitable for use in reactor targets. Dissolving rates were increased under all preparative conditions investigated; density and physical properties were also satisfactory. The oxide retained its improved dissolving characteristics following irradiation in a reactor. The preparation of the ThO2-MgO was demonstrated by the production of 500-lb batches in commercial equipment.