The daily maximum UV-B dose rates during the significant ozone anomalies in October 1992 and March 1993 are calculated relative to the normal conditions of the period from 1979 to 1990. Gridded Total Ozone Mapping Spectrometer data have been used to determine the days with ozone deficiencies below the 2 sigma confidence level. For these days maps of maximum daily UV-B dose rates during these extreme ozone conditions show that UV-B dose rates increased from 10% to 50% at high latitudes. These changes compare well with observations at the Laboratory of Atmospheric Physics, of the Aristotle University of Thessaloniki, Greece and they provide an independent quality assurance and control of the accuracy of coarser model calculations under clear sky conditions. Our analysis shows that the largest increases in the UV-B dose rates during the extreme ozone deficiencies studied are confined to 10 degrees N-40 degrees N in March 1993 and to 10 degrees S to 70 degrees S in October 1992. (C) 1999 COSPAR. Published by Elsevier Science Ltd.