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The acoustic nonlinearity of surface waves is studied to evaluate plastic deformation in aluminum alloys.A narrow-band surface wave is successfully generated by a pulsed Nd-YAG laser system consisting of a beam expander and a slit mask.Various degrees of tensile deformation are induced by interrupting the tensile tests so as to obtain aluminum specimens with different degrees of plastic damage.The normalized acoustic nonlinearity increases as a function of tensile strain.The experimental results show that the acoustic nonlinearity of a lasergenerated surface wave has a good correlation with the level of tensile deformation and has a potential to evaluate microdamage induced by dislocation microplasticity.