Nanofiltration (NF) employs a pressure gradient to selectively transport solvent and certain solutes across a membrane. NF is similar to reverse osmosis, but the membranes used are slightly more permeable, so less pressure (which translates into less energy) is required for the separation. Reverse osmosis generally focuses on the removal of all salts from water, whereas NF is useful for removal of specific salts such as MgSO4. Applications of NF include water softening and removal of pollutants, such as herbicides, from potable water. Our research focuses on developing multilayered polyelectrolytes as high-flux NF membranes. Thus far, we have achieved fluxes that are as much as 3-fold higher than those of state-of-the-art commercial membranes, while still achieving high rejections of SO42- and small organic molecules. For more information on the nanofiltration apparatus see Langmuir, 19, 7038-7042 (2003). Current work focuses on utilizing the wide variety of available polyelectrolytes to achieve even higher fluxes without compromising separations. This research is supported by the Office of Basic Energy Sciences of the Department of Energy.