Disinfection byproducts (DBP) are compounds found in drinking water that can be carcinogenic. DBPs are formed when natural organic matter (NOM) reacts with chlorine, a common disinfectant used in drinking water treatment. While effective treatment strategies exist, none completely remove NOM from drinking water. There are several known factors impacting NOM reactivity and DBP formation, including pH and ion concentrations. However the effect of other NOM characteristics on DBP formation, such as size, is yet to be fundamentally understood. Our research seeks to understand whether NOM size affects DBP formation potential. NOM samples were prepared at known concentrations of 1, 5, and 10 mg/L (ppm) and analyzed for two regulated categories of DBPs, trihalomethanes (THMs) and haloacetic acids (HAAs), to gain a comprehensive baseline. NOM characteristics were also quantified, including size exclusion chromatogram (SEC) to divide known samples by molecular weight into two fractions: >10 and <10 kDa. The resulting DBP species and concentrations were compared to the baseline findings. We hypothesized that larger NOM fractions would have a greater effect on DBP formation due to the greater surface area, allowing for more sites for DBP formation reactions to occur. Preliminary results confirm that increasing concentrations of organic matter increase DBP formation. Ongoing toxicological analysis will evaluate the relative health effects of the different DBP species preferentially formed by disinfection for different size fractions. These findings aim to inform prioritization of treatment strategies to mitigate DBP formation and regulations.