The stratospheric ozone depletion during the last two decades, the increase of UV-B irradiance levels at the ground and the possible impact on the biosphere has led scientists to develop and use instruments of high accuracy for UV measurements. During the last two years, 9 UV stations have been established in different environments in Greece and Cyprus, with the aim to establish a long-term monitoring network. The instruments of the network (NILU-UV multichannel filter radiometers) can provide measurements of irradiance in the UV and the visible part of the solar spectrum. In this study, first results from the calibration measurements and the quality assurance procedures are presented. The stability of the maximum of spectral response and the full width at half maximum was measured within 0.5 nm. Lamp tests were performed and downward drifts up to 40% in UVA channel sensitivity were observed. Calibration factors derived from lamp measurements could provide measurements of UV dose rate and total ozone with quite good agreement when compared with standard ultraviolet instruments.