The chemical reaction of Au and P-type (111) oriented silicon on the surface induced by an acousto-optic Q-switched frequency doubling laser is reported. The samples were analyzed by X-ray diffraction, X-ray photo-electron spectroscopy (XPS), metallurgical microscope, scanning electron microscope (SEM) and four-point probe resistivity measurements. X-ray analysis generally showed the coexistence of non-uniform multiphase au-silicidea since their composition yaryed with depth, i. e., there is a "transition region". This demonstrated that the reaction took place preferentially at the interface between gold and silicon. It is well known that the Au-Si phase diagram has a lowest en tec tic point of 370 ℃ which was determined by extrapolation of the two branches o± the liquidus curve and therefore is rather uncertain. Thus, the gold-silicon reaction produced Au-silicides rather than Au-Si mixture. In this case heating and cooling rates achieved by the scanning beam are of primary importanco.