The process of surface diffusion is the focus of this research project supported by the Analytical and Surface Chemistry Program. In this work Professor George, who has pioneered the application of laser induced thermal desorption methods for the study of surface diffusion, will extend his studies to anisotropic and coverage dependent diffusion using a newly developed linear diffraction technique. This laser induced transient grating method promises to provide wider applicability, and the possibility of monitoring diffusion over a much wider coverage range than previously possible. These methods will be applied to the study of small molecule diffusion on bimetallic surfaces, long chain hydrocarbon diffusion on ruthenium, and to the study of molecular diffusion on ice surfaces. %%% An understanding of the mechanism and rates of surface diffusion of molecules is essential to the understanding of the dynamics of reactions on surfaces. Newly developed transient grating methods will be applied to the study of a range of molecular adsorbates on well characterized surfaces, providing much needed information for the understanding of catalytically relevant surface reactions.