An investigation of the use of KrF pulsed excimer laser surface machining of X-cut lithium niobate is presented. Trenches of 20 mum width were formed using a wide range of laser fluences and number of pulses. These trenches were analysed in terms of ablation rate, ablation depth and in particular, laser-induced surface damage. Different forms of observed surface damage have been analysed using SEM imaging and categorised. Possible mechanisms for the damage types are proposed. The effect of depositing a silicon dioxide overlayer on the sample prior to ablation is examined resulting in significant improvement in the quality of the ablated patterns with minimal reduction of ablation rate. (C) 2002 Elsevier Science B.V. All rights reserved.