Surface conductance measurements, using the transmission line model (TLM) technique, have been used to assess surface electrical damage in GaAs resulting from dry etching. Reactive ion etching (RIE) in CH4/H2and SiCl4, ion beam etching in Ne and Ar and electron cyclotron resonance etching (ECR‐RIE) in CCl2F2/He have been investigated. A phenomenological model is proposed for determining the extent of the surface etching damage. It is found that the use of slow etch rates, high bias/accelerating voltage and light ions in etching increases the electrical damage in GaAs. Possible causes for the creation of deep damage are discussed, and the criteria for low damage etching are suggested. The TLM method is a powerful technique for assessing etching processes used for semiconductors.