Complex mixtures of disinfection by-products (DBPs) are formed when the disinfectant oxidizes constituents (e.g., natural organic matter (NOM) and organic pollutants) found in the source water. Since 1974, over 600 DBPs have been identified in drinking water. Despite intense identification efforts, greater than 50% of the total organic halogen (TOX) formed during disinfection remains unidentified. Concerns for public health continue to drive DBP research as increased exposure has shown to have carcinogenic and/or endocrine disrupting properties. The estimated potency of DBPs investigated either individually or in defined mixtures does not account for the magnitude of effects reported in the positive epidemiologic studies, suggesting the need for toxicological evaluation of whole DBP mixtures, including the unidentified DBPs. Previously, a procedure was developed to chlorinate concentrated NOM solutions to create whole mixtures of DBPs representative of free chlorine systems that was used for health effects research. Extending this previous work, the objective of this project is to create whole mixtures of concentrated DBPs representative of chloraminated systems.