An acid digestion process for reducing the volume and costs for storing waste ion-exchange resins contaminated with radioactive substances has been developed on a bench scale. The study was conducted with nonradioactive resin digested in concentrated sulfuric and nitric acids at temperatures of 255 to 290°C. The residue is comprised of metal sulfates that occupies ∼5% of the original volume. The resin is carbonized by sulfuric acid and oxidized to carbon dioxide and carbon monoxide by both sulfuric and nitric acids. The rates of the four major simultaneous reactions in the digester were determined.