Concentrating photovoltaics (CPV) represent an emerging market at its early stage for terrestrial applications with large growth expectation and considerable research activity on new cell production has been conducting recently. In response to a fast growing demand for traceable and independent measurements on CPV cells and systems the European Solar Test Installation (ESTI) has started a research program on indoor/outdoor devices characterization. This paper focuses on two essential components of device calibration. Calibration requires traceable calibrated reference devices: for this purpose reference c-Si cells equipped with neutral density filters of various optical densities have been used at ESTI for checking device linearity at different concentration ratios. Also essential is the implementation of common procedures and intercomparison of test results at different test laboratories. Procedures and experimental setups for concentrating c-Si cell characterization at both ESTI and at the UTTP FOTO Laboratory of ENEA are described and results of an intercomparison are presented and discussed. Electrical performance measurements have been performed at high intensities on three different setups: a recently developed 1500x pulsed solar simulator at ESTI and two modified solar simulators capable of achieving up to 250x concentration at ENEA. Reported results show agreement within measurement uncertainties of the electrical parameters.