The degradation of trichloroethylene (TCE) to carbon dioxide (CO2) and chloride (Cl-) has been reported to occur during thermal remediation of subsurface environments. The effects of solid-phase composition and oxygen content on the chemical reactivity of TCE were evaluated in sealed ampules that were incubated at 22 and 120 degrees C for periods ranging from 4 to 40 days. For all treatments, no more than 15% of the initial amount of TCE was degraded, resulting in the formation of several non-chlorinated products including Cl-, CO2, carbon monoxide, glycolate, and formate. First-order rate coefficients for TCE disappearance ranged from 1.2 to 6.2 x 10(-3) day(-1) at 120 degrees C and were not dependent upon oxygen content orthe presence of Ottawa sand. However, the rate of TCE disappearance at 120 degrees C increased by more than 1 order-of-magnitude (1.6 to 5.3 x 10(-2) day(-1)), corresponding to a half-life of 13-44 days in ampules containing 1% (wt) goethite and Ottawa sand. These results indicate that the rate of TCE degradation in heated, three-phase systems is relatively insensitive to oxygen content, but may increase substantially in the presence of iron bearing minerals.