The concentrations of bromine and iodine in the USGS marine mud MAG‐1, the NRCC marine sediments BCSS‐1 and MESS‐1, and the NBS estuarine sediment SRM 1646 have been determined by energy‐dispersive x‐ray fluorescence spectrometry. Matrix and intermediate thickness effects were overcome by standard additions to constant weights of each sample. 3‐sigma detection limits are 6 ppm Br and 24 ppm I. There is a need for many more analysts to report their results before “usable values’can be established for these elements in marine sediment refer