The potential of optical remote sensing for monitoring deforestation in tropical areas has been demonstrated. However, the important cloud coverage limits its application on large areas. A new receiving station for SPOT and ENVISAT images is operational in French Guiana since February 2006 in the framework of SEAS-Guyane Project coordinated by IRD. The benefits of this new ground station are decisive, for they drastically extend the capacity of acquiring images over the whole Amazonian and Caribbean region due to efficient gathering of multi-source satellite data sets in heavily clouded areas, for specific scientific, public or commercial purposes. On this basis, a very first SPOT mosaic of French Guyana was produced for year 2006, combining all available images from SPOT 2, SPOT 4 and SPOT 5 sensors. A spatio-triangulation on a block of the 46 less cloudy images was applied and images were orthorectified using the software GeoView (from IGN, French topographic institute). The result is a high resolution image covering the entire French Guiana with state-of-the-art cartographic precision. A cloud screening was applied on this mosaic, and 132 complementary scenes were used to fill the gaps of the residual clouds present in the image. The final result is a near cloud-free orthomosaic of French Guyana in 20-meter resolution which was used in partnership with IFN to estimate land use areas and changes as expected in the framework of the Kyoto protocol and the UNFCCC convention on climate change. From now on, this mosaic will be upgraded with SPOT 5 images, harvested from SEAS and which are of major interest for monitoring regional environmental conditions. The tools and methods developed to compute this first SPOT mosaic over French Guiana could be transferred to other countries confronted with the same difficulties in monitoring tropical forest evolution under heavy cloud cover.