Microfiltration (MF) and ultrafiltration (UF) membrane processes are at a critical stage in their development. The water treatment community needs to consolidate the dispersed knowledge on these processes into a single source that can be readily used as a reference to support the transition of membrane technology to large-scale applications (greater than 100 MGD). In addition, water systems considering smaller applications need a single, reliable and usable source of information on existing membrane installations to support informed decisions when determining the suitability of membranes for their purposes. In order to respond to these needs, a low-pressure membrane knowledge base is being developed. The knowledge base will provide the drinking water community with an invaluable tool to accomplish these important objectives. The knowledge base will consolidate the diverse information on the use of low-pressure membranes into a single source and will include the results of a survey of existing MF/UF plants located throughout the world with capacities greater than or equal to 1 MGD (4,000 m3/day). The project team has identified more than 130 membrane plants from all major membrane manufacturers that qualify to participate in the survey. AwwaRF is providing funding for the knowledge base project. This paper presents the tasks in the development of the MF/UF knowledge base and the results to date. Includes figures.