Ozone measurements from the Total Ozone Mapping Spectrometer on the Nimbus 7 satellite are compared with ground-based measurements from five Dobson stations at northern latitudes to evaluate the accuracy of the TOMS data, particularly in regions north of 50¿N. The measurements from the individual stations show mean differences from -2.5% up to +8.3% relative to TOMS measurements and two of the ground stations, Oslo and Longyearbyen, show a significant drift of +1.2% and +3.7% per year, respectively. It can be shown from nearly simultaneous measurements in two different wavelength double pairs at Oslo that at least 2% of the differences result from the use of the CC' wavelength double pair instead of the standard AD wavelength double pair. Since all Norwegian stations used the CC' wavelength double pair exclusively, a similar error can be assumed for Troms¿ and Longyearbyen. A comparison between the tropospheric ozone content in TOMS data and from ECC ozonesonde measurements at Ny-¿lesund and Bear Island shows that the amount of tropospheric ozone in the standard profiles used in the TOMS algorithm is too low, which leads to an error of about 2% in total ozone. Particularly at high solar zenith angles (>80¿), Dobson measurements become unreliable. They are up to 20% lower than TOMS measurements averaged over solar zenith angles of 88¿ to 89¿. ¿ American Geophysical Union 1992