In May 1997 long-term measurements of spectral resolved UV-B irradiation (wavelength range of the instrument 280 to 322 nm) at the NDSC-Station in Ny-Ålesund (Spitsbergen) were started using a self-developed very fast multichannel spectroradiometer. In March 1998 a multichannel UV-A spectroradio-meter was installed at Ny-Ålesund to supplement the spectral range of the measurements from 318 to 400 nm. For the evaluation of the data with regard to changes in total ozone the ratio of the measured irradiation at two wavelengths (300 nm / 320 nm) has been used to minimize the influence of other atmospheric parameters like clouds or aerosols. This ratio, called ozone index, is compared with ozone sonde data as well as daily TOMS data of total ozone. This comparison shows a good anticorrelation between the irradiation at short wavelengths and total ozone. Apart from ozone, influences of clouds and varying ground albedo have been investigated. The evaluation of the UV-B Data has been supported by radiative transfer modeling.