An efficient transformation procedure has been developed on a hybrid larch embryogenic line using Agrobacterium tumefaciens as DNA transfer vector. A neomycin phosphotransferase (neo) gene under the control of the 35S CaMV promoter with a double enhancer allows us to regularly obtain selective multiplication of resistant calli. Several factors involved in the different steps of the procedure have been tested for their capacity to increase transformation efficiency. After three months on selective medium the transgenic calli remain embryogenic and transgenic plants can be acclimatized easily in the greenhouse. Stable integration of the transgene has been confirmed by PCR and Southern hybridization on transformed calli and acclimatized plants. This improved transformation procedure allows us to regenerate in routine at least five independant transformants per Petri dish of embryogenic calli (300 mg fresh material). Moreover, this procedure has been successfully applied to three other embryogenic lines. This opens the way for the introduction of genes of interest into a conifer species.