Monte Carlo simulations of the electron drift response to an ac-electric field are used to calculate the power dependent third harmonic generation efficiency for far-infrared radiation. The results are compared with far-infrared frequency tripling experiments. It is shown that the nonlinear optical properties are much more sensitive to parameter changes in the Monte Carlo simulation than conventional drift velocity results. Hence, this is a sensitive method to test Monte Carlo transport simulations. (C) 1996 American Institute of Physics.