The theory of second‐harmonic generation of light was examined with particular emphasis on the saturation effects occurring at high laser power levels. The nonlinear coupled Maxwell's equations were solved approximately to yield solutions of simple form. The effect of beam divergence was taken into account by averaging the solution over the entire angular spread of the laser beam. The second harmonic thus generated is seen to be proportional to the32power of the laser power independently of the length of the crystal in long crystals. Experimental data in good agreement with the theory are presented.