With the promulgation of the Stage 1 Disinfectant/Disinfection Byproduct (D/DBP) Rule and the future promulgation of the Stage 2 D/DBP Rule, utilities are facing the challenge to select distribution system sites representative of worst-case conditions in terms of high trihalomethane (THM) and haloacetic acid (HAA) concentrations, high and low disinfectant residuals, and a range of hydraulic residence times. The US Environmental Protection Agency (USEPA) recently developed a Guidance Manual to help the utilities select their distribution system sites for the Initial Distribution System Evaluation (IDSE). Our team is currently working on an AwwaRF research project that studies factors affecting formation and decay of DBPs under actual distribution system conditions. While the goal of the USEPA Guidance Manual for IDSE is to help utilities select DBP monitoring sites in a full-scale distribution system, our study focuses on a relatively small area of the system to allow a comprehensive investigation of the factors affecting the formation and decay of several DBPs (THMs, HAAs, NDMA). Thus, the first step of our project consisted of selecting a general distribution system area for each utility. Once a distribution system area was identified, modeling was conducted to calculate the hydraulic residence time (water age) associated with each node in the distribution area. Monitoring sites were then selected based on water age and other hydraulic and water quality parameters. Five geographically-spread utilities are participating in our project. This paper provides an overview of the regulations affecting distribution systems, and describes in detail the methodology used and the factors affecting the selection of distribution system sites used to monitor for THMs and HAAs under the Stage 2 D/DBP Rule. Includes figures.