This paper describes the development of an approach for the bench-scale testing of nanofiltration. A rapid bench membrane test (RBSMT) was designed to capture critical aspects of full-scale systems, especially water flux and solute rejection, while maintaining the benefits of a bench-scale system such as small test water volumes, ease of operation and flexibility. In order to achieve these objectives, the RBSMT was designed around a tangential-flow membrane cell utilizing a 24 square inch membrane sheet. It is operated with the feed spacers and permeate carriers used in full-scale spiral-wound elements, making the unit hydraulically similar to a differential element of a full-scale module when operated at appropriate cross-flow velocity. A recycle loop was employed so that a realistic recovery might be utilized while maintaining the appropriate cross-flow velocity.