Experimental results on harmonic generation and parametric mixing of surface acoustic waves are reported. Harmonics of signals at 615 MHz and 1.69 GHz propagating on YZ LiNbO3substrates were observed: the experiments on parametric mixing used two surface acoustic waves atf1=490 MHz andf2=1.09 GHz. Optical probing technique was used to observe directly the spatial variations of the harmonics, the sum, and difference frequency signals. It will be shown that the nonlinear interactions can be phenomenologically described by coupled amplitude equations. The nonlinear coupling constants are determined by comparing the experimental results with the calculations.