This slide presentation outlines regulatory information, guidance and key results from a study investigating the formation and decay of disinfection byproducts (DBPs) in five full-scale distribution systems (DSs). This paper also presents decision tools to select DS monitoring sites to comply with the Stage 2 Disinfectants/Disinfection Byproduct Rule (DBPR). Topics covered include: the four key components of the Stage 2 DBPR; initial distribution system evaluation (IDSE); System Classification and IDSE Schedule; IDSE Options: Standard Monitoring Program (SMP) or System-Specific Study (SSS); SMP sampling locations; schedule of SMP sampling; SSS using historic DBP data; SSS using water DS model; SSS using alternative options; reporting for IDSE; key objectives of AwwaRF/USEPA Project 2770 - "Formation and Decay of DBPs in the DS"; selection of participating systems, sampling locations; and, key findings of the study.