Two alkali-tin-silicate (ATS) glasses have been prepared at Argonne National Laboratory (ANL) as part of our ongoing research in radioactive waste glass development. These glasses dissolved 5% and approximately 7% Pu. Early corrosion test results indicate that Pu-bearing ATS glass is extremely durable. The initial goal in this project concerned equally both the solubility of Pu and the durability of the ATS glasses; however, our primary emphasis has changed recently to maximizing the loading of Pu in the glass. ATS-based glasses, using Th(VI) and Ce(III) as surrogates for Pu(IV), are now being investigated to increase the solubility of Pu without substantially sacrificing the durability of the current ATS formulations. The solution data from various corrosion tests on the original Pu-containing ATS glasses are also presented.