Gene assisted selection for wood quality and end-use properties require a better knowledge of the molecular mechanisms involved in the formation of secondary xylem (wood). We characterized wood forming samples of maritime pine collected during a growing season and along a cambial age gradient at the anatomical and chemical levels. The variability found within a single individual led us to hypothesize that this plasticity can result from the differential expression of genes/proteins during wood formation. SSH libraries were first generated to identify the most representative genes of each type of wood (early, late, juvenile, mature wood) as well as those that are specific to differentiating xylem. Second, a microarray was established based on 11,000 unigenes derived from 27000 ESTs. In this poster we will review the main results of this transcriptomic study aiming at providing expressional candidate genes that are being validated by reverse and forward genetic approaches.