There is a renewed interest in disinfection with chlorine dioxide in the United States because of upcoming Federal regulations on disinfection by-products. Bench studies and field applications of chlorine dioxide have shown that it is an effective biocide that does not produce halogenated by-products such as trihalomethanes. There are some health concerns with ingesting chlorine dioxide and its metabolites, chlorite and chlorate, and concerns about tastes and odors. These concerns may be alleviated by removing the chlorine dioxide species with granular activated carbon or reducing them to chloride before water distribution.