Both the proposed USEPA Disinfectant/Disinfection By-Product and Enhanced Surface Water Treatment rules have provisions for minimizing the formation of undesirable precursors to disinfection by-products (DBPs) in drinking water. Natural organic matter (NOM) in natural waters contains many of the precursors to the DBPs formed following disinfection of drinking water. DAX-8 resin procedures were used to isolate and fractionate NOM into six fractions; hydrophobic acid, hydrophobic base, hydrophobic neutral, hydrophilic acid, hydrophilic base and hydrophilic neutral. The reactivities of the fractions to the formation of chlorination DBPs are discussed. Aluminum sulfate (alum) jar coagulation tests were performed to determine the optimum coagulation ranges of each fraction. Different levels of pH, fraction concentrations, and coagulant levels were used in the experiments. Given the reactivities of the individual fractions to the formation of selected DBPs (i.e. trihalomethanes, haloacetonitriles, haloacetic acids), one can optimize on the removal of problematic fractions. Hence, if minimization of DBP formation was solely due to specific removal of precursors, microbial inactivation issues would be resolved due to the fact that CT may be increased without an increase in DBP formation.