Bromate can be formed as a by‐product of ozone treatment that is sometimes used for the disinfection of municipal water supplies and bottled waters. The US Environmental Protection Agency has proposed a maximum contaminant level (MCL) of 10 μg/l for bromate in public drinking water. Should the proposed MCL for bromate become final, it may then be considered for adoption as a bottled water quality standard by the US Food and Drug Administration. This paper reports the development of a gas chromatographic/ mass spectrometric (GC/MS) method for the determination of parts‐per‐billion (μg/l) levels of bromate (BrO−3in bottled water. The GC/MS method was validated by using distilled and deionized Milli‐Q® water; detection limits, quantitation limits, and recoveries were determined and identities were confirmed by MS on the basis of analyses of test portions fortified with BrO−3at 0.8, 3.8, 7.7, 15, and 46 μg/l. The method also was evaluated on the basis of recoveries determined for two commercial brands of bottled water fortified with BrO−3at 3.8 and 7.7 μg/l and two commercial brands fortified at 0.8, 3.8, and 7.7 μg/l. For the Milli‐Q® water, recoveries ranged from 100 to 121%; for the fortified commercial products, recoveries Tanged from 87 to 115%. The limits of detection and quantitation were determined to be 0.4 and 0.7 μg/l, respectively. Several commerical brands of bottled water were analysed, and BrO−3was found in these products at levels ranging from none to 38 μg/l.