This paper outlines typical steps for selecting an appropriate membrane process and describes several types of bench and pilot tests to assist in membrane selection, along with their respective benefits and limitations. Methods for selecting a particular manufacturer's membrane product, within a process technology category, however, is not discussed. A membrane process selection chart is a flow chart that asks a series of yes-or-no questions and leads the reader to another question or to the proper type of membrane filtration (nanofiltration, microfiltration, electrodialysis reversal, or reverse osmosis) to use. The decision process is discussed in the text, followed by a comparison of bench testing and pilot testing and which type of testing to use when. A figure shows pressure-driven membrane pilot test options.