X-Ray fluorescence spectrometry is well suited to the determination of elemental composition of air pollution particulate samples because no sample preparation is required for filter collections. 100-second detection limits are 1 to 100 ng/cm squared for most elements of interest, the technique is nondestructive and 10 to 20 elements can be measured simultaneously using presently available commercial equipment. The best detection limits are achieved by reducing the background primary radiation scattered into the measuring system by the sample and its filter substrate. In this work, comparisons were made among various excitation sources, X-ray tubes, fluorescers, radioisotopes and 5- MeV protons and alpha particles, and between wavelength dispersion using a crystal spectrometer and energy dispersion using a Si(Li) solid state detector. Incinerator and other actual samples are analyzed to show applications of the method.