Since July 1995, the Global Ozone Monitoring Experiment (GOME) onboard ESA's 2nd European Remote Sensing Satellite (ERS-2) provides continuous spectral measurements of nadir backscattered earth radiances and solar irradiances in the UV/visible wavelength range. From these, column amounts of sulfur dioxide have been derived for the December 1996 eruption of Nyamuragira volcano, Zaire, and the ongoing activity of Popocat¿petl volcano, Mexico. Maximal column densities of 33 DU for Nyamuragira and 6 DU for Popocat¿petl have been found. Popocat¿petl results compare well with the activity reported for this volcano. Furthermore, GOME observed enhanced SO2 over Southeast Europe which is attributed to lignite combustion in local power plants. The results demonstrate a high sensitivity and specificity of this new sensor for sulfur dioxide. For cloud-free scenes at low solar zenith angles, the detection limit for SO2 is estimated to be 0.4 DU. ¿ 1998 American Geophysical Union