The Project Definition Rating Index (PDRI) is a weighted score sheet used for determining the level of scope definition of building projects during preproject planning, e.g., during conceptual design, schematic design and design development. Developed by the Construction Industry Institute (CII) in 1999, this tool has been widely adopted by various owners and contractors in the building industry. Using the PDRI while conducting planning charrettes (i.e., intense focus meetings involving key stakeholders) provides a collaborative environment that has been shown to significantly enhance the preproject planning process by integrating the perspectives of the various project participants. This paper will give background of the PDRI and its benefits for the project. It will then discuss usage of the PDRI in planning charrettes, including real project examples. The planning charrette process will be outlined, including key participants, required resources and outcomes. The benefits of planning charrettes will be discussed, including key findings. Finally, recommendations will be given to project professionals concerning the use of the charrette approach for planning.