Attenuated total reflection has been characterized as being essentially a surface effect. One implication of this is that for a given analysis only a fraction of a milligram of material properly presented to the totally reflecting face is required to produce a good spectrum. Membrane filters, because of their surface retention ability, not only accomplish a separation of particulate material from fluid media but also permit a nearly ideal presentation of the sample to the ATR crystal. In addition, substrate interferences which complicate transmission results, are reduced considerably. This method is especially valuable where the material to be examined is present in very low concentrations normally difficult to isolate from the fluid media or of a microscopic particle size. Several diverse examples are described which illustrate the utility of the technique.