Ozonation of waters containing bromide ion leads to the formation of organic and inorganic by‐products. By‐product formation is influenced by bromide ion concentration, the source and concentration of organic precursors, pH, ozone dosage, temperature, and alkalinity. Both organic and inorganic by‐products increased when bromide ion concentration increased but decreased with an increase in alkalinity. Organic by‐products were found to increase with a decrease in pH, whereas bromate formation was favored by a high pH. In general, bromoform concentration first increased, then diminished, as the dosage of ozone was increased. Both ozonation and incubation temperatures had a positive effect on the formation of bromoform and bromate. PEROXONE appears to favor bromate formation over organic by‐product formation, whereas the addition of ammonia reduces both bromate and organic by‐products.