The Global Ozone Monitoring Experiment (GOME), launched on the ESA ERS-2 satellite in April 1995, measures solar back scatter spectra from which atmospheric BrO columns may be derived globally with high precision (slant column uncertainties of ¿3¿1013 cm-2 or less). Obtaining such precision requires additional characterization of GOME spectra, reference spectra that are well calibrated in wavelength, and a fitting method capable of reproducing measurements to several parts in 104. This paper describes these elements of the data processing and gives examples of BrO distributions in the stratosphere and enhanced tropospheric BrO in the polar springtime.