The objective of this research was to examine the impact of a magnetic ion exchange (MIEX) resin on subsequent ozonation of drinking water. The resin removes organic carbon and bromide ion from raw drinking water, thus lowering the ozone demand of the water and its bromate formation potential. Several model and real raw drinking waters containing different bromide ion concentrations and different total organic carbon (TOC) levels were treated with various doses of the MIEX resin using jar test procedures to select the optimal resin dosage based upon the removal of ultraviolet (UV)-absorbing substances, TOC, and bromide. The waters were then ozonated in a semi-batch reactor and the formation of bromate and the removal of UV-absorbance were evaluated as a function of ozone dosage and contact time. The results were compared to those obtained by ozonating the water without MIEX-pretreatment. The results show that pretreatment of the waters with the MIEX resin substantially removes UV-absorbing substances and removes bromide; the extent of bromide removal is related to the presence of competing anions such as bicarbonate and carbonate. The ozone demand of the waters was reduced substantially as a result of the removal of organic material by pretreatment with the MIEX resin. Bromate formation was lowered only in those cases where bromide removal was achieved by resin pretreatment. In the cases where bromide removal was minimal, i.e. in waters with high alkalinity (high bicarbonate and carbonate concentrations), the extent of bromate formation was the same as in the controls which were not pre-treated with the MIEX resin, despite the lowered UV-absorbance and reduced ozone demand of the water. Includes 12 references, tables, figures.