The objective of this investigation was to examine the effectiveness of amagnetic ion exchange resin (MIEX(R)) to enhance the coagulation of disinfectionbyproduct (DBP) precursors. The MIEX(R) resin purportedly adsorbs natural organicmaterial, thereby lowering the coagulant demand of the water, as well as loweringits DBP formation potential. Pretreatment of raw drinking waters with MIEX(R) wasevaluated to determine its impact on subsequent coagulation of raw drinking waterwith alum and on subsequent DBP formation following chlorination. Includes 7 references, tables, figures.