Preliminary pilot-scale investigations demonstrate that nanofiltration and reverse osmosis membranes can effectively remove methyl tertiary-butyl ether (MTBE) and perchlorate form the Metropolitan Water District of Southern California's source waters. Nanofiltration and reverse osmosis membranes consistently removed greater than 97% and 80% of the applied MTBE and perchlorate, respectively. Examination of results for ultraviolet light absorbed at 254 nm (UV254), total organic carbon (TOC), conductivity, turbidity, and particle count data indicated that both membranes produced permeates with acceptable water quality. However, low toluene levels were detected in the permeate produced from both membranes from MTBE rejection studies. Includes 14 references, tables, figures.