The temperature dependent etching of GaAs and InP using both molecular and remote plasma activated Cl2 and HC1 is examined. GaAs etches nearly three times faster in a remotely generated C12 plasma than in a molecular Cl2 environment with plasma off. The temperature dependance from room temperature to 250°C is similar for both cases. Significant etch rates of GaAs are observed for HC1 remotely generated plasma even at room temperature (∼1000 Å/min). Although the etch rate for InP below 150°C is quite low for either C12 or HCl, the relatively fast, temperature independent etch rate above this temperature is comparable to that of GaAs. The results are compared to RIE and a thermodynamic model.