This paper presents a study of the ion‐enhanced etching of InP by Cl2using a modulated ion beam technique, in which pulses of rare gas ions impinge on an InP surface with coincident Cl2and the resultant products are detected with a mass spectrometer. The stoichiometry of these products and the dependence of the ion enhanced etching on InP temperature and chlorine pressure are compared to the thermodynamically predicted chemical etching of InP by Cl2. The dependence of the ion‐enhanced etching on ion current, ion energy, and ion mass are compared to the dependence on these parameters observed in the physical sputtering of InP. The experimental results are discussed in relation to a model in which the incident ion creates a transient thermal pulse (∼100 ° K) which causes the desorption of the relatively volatile indium chlorides from the surface. Of particular technological importance is the fact that large chemical enhancements over physical sputtering (>100/1) are possible with such a mechanism.