The effect of temperature on the volatilization of ruthenium, technetium, and selenium was observed in calcination experiments with simulated high-level liquid waste. Technetium and selenium were more volatile as calcining temperature increased. Ruthenium was less volatile when temperature exceeded 300degC. More than 80% of ruthenium that volatilized from room temperature to 500degC occurred between 200 and 300degC. A small amount of ruthenium volatilized above 300degC as well as below 135degC. (author).