Ozonation of natural waters containing bromide ion leads to the formation of inorganic hypobromite and bromate and many brominated organic byproducts, only a few of which have been identified. The study described here identified bromoform, bromoacetonitriles, bromoacetone, bromoacetic acids, and a group of labile compounds referred to as bromohydrins. These byproducts are reactive toward most quenching agents used for their stabilization. Dissolved organic bromide (DOBr) formation was favored by a low pH, low alkalinity, and low ammonia concentration and increased as a function of bromide concentration in the raw water. A mass balance of bromide indicates that, in some cases, < 10 percent of the DOBr content has been identified. Includes 26 references, tables, figures.