We report excimer laser induced etching of GaAs samples covered with a layer of condensed Cl2. The experiments were performed at low temperatures (120-150 K) and in a chlorine ambient (PC12=1-40 mTorr). Spatially well-resolved, anisotropic etching has been demonstrated with an observed etch rate of 0.25 Å/pulse (0.1 μm/min for typical parameters). The etch rate is characterized as a function of the various system parameters (pressure, temperature, laser rep-rate, etc.), and a model is proposed to describe the etching mechanism.