In the framework of a pilot project of the Commission of the European Community concerning the application of remote sensing techniques for agricultural statistics, a specific study of an area in Northern Greece is being carried out at the Joint Research Centre, Ispra. This study involves the use of multi-temporal TM and SPOT data, in order to combine the spatial resolution of SPOT with the spectral resolution of TM and to gain in flexibility for the choice of dates. This approach is expected to overcome ambiguities in the spectral definition of crops, but significant problems are introduced, due mainly to the different atmospheric conditions present at the various dates. A study of the effect of the various factors on the spectral response of the crops will help to define a classification criterion based on their phenological variation.