Comparisons between primary instruments are of paramount importance to ensure reproducibility of measurements and reliability of calibrations and are expressly required for laboratories applying the quality work scheme outlined in IEC / ISO 17025. The correct and reliable measurement of the spectral content of the light sources used is crucial in the calibration process of a generic photovoltaic (PV) device; this requirement has become increasingly important since technological differences have increased in the world of photovoltaics. The two issues mentioned above were the main reasons behind the creation of a European and international network consisting of laboratories and industries in the PV field willing to share best practices in the calibration and measurements of spectroradiometers, as well as to check periodically for discrepancies in the measurement of the spectral content of solar radiation. This paper reports the preliminary results of spectroradiometer comparison performed by measuring direct normal solar spectral irradiance and spectral irradiance under an artificial light source with AM0-like spectrum.