The main goals of this ongoing research are to develop methods for characterizing natural organic matter (NOM) from aqueous sources using capillary electrophoresis (CE) and to use these methods to evaluate the impact of NOM composition on important environmental reactions. Specific objectives include: develop a method for characterizing NOM by testing various modes of CE operation using model macromolecules and standard NOM samples; use CE and more traditional NOM characterization methods to evaluate the composition of a variety of NOM sources representing a broad spectrum of NOM types; and, develop correlations linking NOM composition to reactivity with chemical oxidants. Development of correlations linking the rapid analysis of NOM composition by capillary electrophoresis with NOM reactivity will reduce the costs and improve the speed at which we can predict the potential impacts of NOM on drinking water quality and public health. Information on NOM composition and reactivity also will be useful for selecting appropriate treatment strategies to control disinfection byproduct formation and regrowth. Preliminary results from this research are presented and discussed. Includes 28 references, table, figures.