Dynamic process models, which facilitate the design of activated sludge systems, require numerous input parameters that characterize the influent wastewater and define the various kinetic and stoichiometric relationships of biological processes. Whereas kinematic and stoichiometric parameters remain relatively constant among municipal activated sludge systems, enabling the utilization of default values for these parameters, wastewater characteristics vary significantly and often must be independently evaluated to obtain valid model predictions. Critical wastewater characterization parameters, particularly for biological nutrient removal (BNR) systems, are COD partitioning and specific nitrification rate, uA. Results for these critical parameters, as well as TKN partitioning and VFA content, are reported for the Metropolitan Wastewater Treatment Plant, St. Paul, Minnesota. Recently developed experimental procedures incorporated into the wastewater characterization program include the SBR protocol (Dold, 1992) and flocculated COD analysis (Mamais et. al., 1992).