Different leaching tests (MCC-1 and MCC-2) have been conducted on a monolithic sintered modified SYNROC-B ceramic waste form containing 10 wt% simulated high-level radioactive waste in triple distilled H2O. The temperature range was 25 to 150°C. Increases in the leach rates of cesium and barium have been observed as the leaching temperature increases indicating that the leach rate should follow the empirical Arrhenius law:LRi(t) =Ki exp (-Qai/ Rt) ,where LRi(t), Ki, and Qai are the leach rate, the experimental constant, and the activation energy of the element of interest, i. The activation energies for cesium and barium are 6.62 and 3.2 kcal.mol-1, respectively. The behavior of the pH of the leachant was monitored as a function of leaching time and temperature. Increases in the fluorine ion concentration (F-) in the leachant were found to be temperature-and time-dependent functions indicating the leaching of the Teflon containers recommended by the Materials Characterization Center. These Teflon containers should be preleached before their use in leaching experiments, or other leach-resistant containers should be used.