Recent re-interest in slow sand filtration was brought about by the needs for small communities to install treatment technologies that are effective, less costly, and easier to operate and maintain than the more sophisticated rapid sand filters. These simpler technologies for small communities can easily be adapted and used in developing countries to provide safe drinking water. The United States Environmental Protection Agency (EPA) recently re-investigated slow sand filtration as a simple technology for treating drinking water. Two pilot scale filtration systems (a slow sand filter, and a second slow sand filter in parallel with a slow-rate filter containing granular activated carbon) were set up and monitored under controlled conditions. In addition to the inhouse studies, EPA funded several field projects to further evaluate the effectiveness of slow sand filters and to examine operation and maintenance costs and labor requirements.