This document summarizes the current national statistics for small drinking water systems (serving less than ten thousand people). It describes the current status of regulations, treatment technologies, source water issues, distribution system characteristics, waste residual issues, security/emergency response, and monitoring as they pertain to small systems. The objective of this document is to provide researchers in the Water Supply and Water Resources Division in the National Risk Management Research Laboratory with a basis to design and implement future research projects that will focus on the most pressing needs of small systems. The majority of this report includes data and information acquired between June 1, 2004 and October 1, 2005, and most of the work was completed on November 1, 2005. Section 5.6, which is related to small systems treatment options on affordability and provides a definition of 'unreasonable risk to health,' presents more recent updates (performed in August 2006) based on reviewer comments.