The quantitative determination of mercury at parts per billion levels in the environment has become increasingly imperative as research continues to document the toxic effects of trace levels of mercury, especially when converted to an organic form. In order to obtain reliable analyses for low mercury levels, the capabilities of essentially all applicable analytical instrumentation have had to be extended by the use of chemical separating and concentrating procedures. An effective and yet simple concentrating technique for trace metals involves the use of resin-loaded papers. These papers consist of approximately 50 percent cellulose and 50 percent powdered ion-exchange or chelating resin material. A resin-loaded paper may be used as a very short ion-exchange column (the thickness of construction paper) where a solution is filtered several times through the paper to obtain quantitative collection of the elements of interest; or the paper may be simply suspended in a solution, relying on diffusion of the collectable ions to the resin-loaded paper. In either case, the trace elements of interest are concentrated from a large volume into a volume more amenable to instrumental determination. Of equal importance, the desired elements are separated from the bulk matrix, thereby reducing interference problems. Both of these accomplishments result in increased analytical sensitivity. In the case of mercury, the added capability of distinguishing between organic and inorganic forms makes the use of resin-loaded papers highly inviting.