Abstract Seven filter substrates, representing both fiber and membrane construction, have been studied for their utility in quantitative X-ray diffraction analysis. Filter material densities, indices of refraction, specific mass densities, mass absorption coefficients, and various properties relative to X-ray diffraction from the loaded filters have been determined. The degree to which these filters are suitable for quantitative X-ray diffraction is primarily dependent upon (1) interfering background scatter; and (2) the mass per unit area of the paniculate load collected. Teflon filters have proven to be superior to all others for specific mass loadings of less than 200 μg cm −2. For mass loadings greater than 300μg cm −2, the ‘quartz’ or glass fiber filters provide the most suitable substrate, primarily because of the better particle retention qualities and the lack of a substrate spectrum in the diffraction pattern.