The reactive ion etching of p-InGaP and p-GaAs using CH4/H-2 was examined through design of experiment techniques. The etch rate of InGaP and GaAs, the etch rate ratio of InGaP over GaAs, and the de bias were optimized by fractional factorial design as a function of total gas flow rate, methane composition, total pressure, and rf power. It was found that the rf power and the total chamber pressure were the most significant parameters in the reactive ion etching process. Models were created to describe the change of each response over a range of etching parameters.