This article discusses the new Stage 2 Disinfectants/Disinfection Byproducts Rule that essentially seeks to prevent delivery to some customers of tap water that regularly contains disinfection byproducts (DBPs) in amounts that exceed standards as measured on a systemwide basis. To meet this objective, the Stage 2 D/DBPR requires community water systems and nontransient-noncommunity water systems that use surface water or groundwater and add disinfectants other than ultraviolet light or deliver water treated in such a manner to: comply with standards for total trihalomethane and five haloacetic acids on a locational running annual average (LRAA) basis rather than on a systemwide running annual average (RAA) basis; monitor at distribution system sites where DBP levels are at their highest rather than where water resides the longest; and, sample according to a schedule that targets peak occurrence times rather than be allowed to avoid such times. The Stage 2 rule aims to strengthen the Stage 1 rule by requiring a two-phased transition over nine years that will have all systems start by conducting an initial distribution system evaluation (IDSE) to identify the best monitoring sites, simultaneously comply in three years with State 1 RAA standards and "transitional" Stage 2 LRAA standards at Stage 1 monitoring sites, and eventually switch to complying only with final Stage 2 LRAA standards at IDSE-identified monitoring sites. Includes table.