In October 2001 the City of San Diego and Montgomery Watson Harza were awarded a grant from the Bureau of Reclamation to evaluate membrane bioreactor (MBR) technology and its potential application to wastewater reclamation. Accordingly, four leading commercially available MBR systems are being operated at the pilot scale level over a 14-month period at the Point Loma Wastewater Treatment Plant located in San Diego, CA. The four MBR systems being tested include Kubota, US Filter / Jet Tech, Zenon and Mitsubishi Rayon. While the latter two systems are well established in the US, the former two systems are currently being introduced to the US market. Accordingly, a primary objective of this study is to evaluate the performance of the new systems, which will in turn provide useful information to utilities considering MBR technology for wastewater reclamation. A second objective of the study is to compare the performance of the MBR systems during operation on raw wastewater as opposed to primary treated effluent. While past studies conducted by the project team have shown the feasibility of MBR technology for water reclamation using raw wastewater, the use of primary treated effluent has not been tested. Because primary treated effluent contains a lower amount of organic matter and solid content than raw wastewater it may be possible to operate the MBR systems in a more efficient manner which would result in overall cost reduction for water reclamation using MBR technology. Includes figures.