Thermogravimetric studies were made on thin layers and spherical pellets of decopperized anode slimes. These have shown that deselenization proceeds initially by the volatilization of the free selenium content at about 360°C. At higher temperatures and under an oxidizing atmosphere, silver selenide is decomposed either directly or via the formation of silver selenite and its subsequent decomposition. The rates of these reactions depend greatly on the concentration of selenium dioxide in the atmosphere over the reacting surface. It has been shown that the deselenization of slime pellets is enhanced when a forced air flow over the reacting particle is provided. This will promote oxidation, remove the selenium dioxide product to minimize the formation of silver selenite from silver and selenium dioxide, and increase the rate of decomposition of the silver selenite formed.