Since the development of brackish water reverse osmosis (RO) membranes their use has seen rapid development. All major RO membrane manufacturers have developed one or more brackish water RO membranes. In the last ten years these membranes have seen a large decrease in price and an increase in productivity making brackish groundwater desalination an attractive option in water scarce regions. The latest generation of brackish water RO membranes has shown marked improvements in terms of operating pressure and this could translate into lower costs for brackish water treatment. This paper presents the results of pilot testing conducted on these new generation low pressure brackish water RO membranes for groundwater desalination. Two new membranes were tested - ESPA 4 manufactured by Hydranautics, Inc, Oceanside, CA and 4040 BL manufactured by Saehan Industries, South Korea. Hydranautics, Inc. is a well established membrane manufacturer in the US while Saehan Industries does not currently have a presence in the US market. An older generation membrane (ESPA 2 from Hydranautics) was also operated in parallel with the new generation membranes to provide baseline data for comparison. This project was conducted as a part of a research program initiated by Desalination Research and Innovation Partnership, which consists of water purveyors in the Southern California region. Includes tables, figures.