Genetic transformation of two woody species: poplar and larch. Poplar is a model for studying gene expression in trees. A transformation procedure involving Agrobacterium tumefaciens as a vector for DNA transfer has been optimized on modele clones and used to produce transgenic plants that have been transferred to the greenhouse. Marker genes as well as genes potentially able to improve insect resistance or to alter lignin metabolism have been introduced into poplar and the transgenic trees have been characterized and allowed us to assess the validity of a genetic engeneering approach on trees. Field trials involving transgenic trees has been set up in order to follow the stability of transgene expression at various time of the year and to validate the results obtained in the greenhouse. Also, we are currently improving transformation protocoles on poplar clones of economic interest. Likewise, a transformation procedure has been developed on hybrid larch embryonal masses using Agrobacterium tumefaciens. After cocultivation, the transgenic material remains embryogenic which allows production of transgenic plants in the greenhouse. Stable integration of the transgene has been confirmed by molecular analyses. Illustration on these different topics will be presented.