Single-layer films and multiple-layer films can be quantitatively analyzed using X-ray fluorescence. Due to the absence of adequate standards, most methods are based on the calculation of theoretical X-ray fluorescence intensities from fundamental parameter methods. These methods require as initial estimates the exact qualitative sample structure and accurate starting values for both concentrations and layer thicknesses. This paper proposes a fundamental parameter method that uses a genetic algorithm as an optimization procedure. The relaxation of the requirements on the description of the sample due to this robust optimization is discussed. Preliminary results are presented indicating possible applications as well as areas for further research.