Leaf discs of grapevine cv. Seyval blanc originating from in vitro cultures were transformed with Agrobacterium tumefaciens strain LBA 4404 harbouring the vector pGJ42 carrying genes for chitinase and RIP (ribosome-inactivating protein) in an attempt to improve fungal resistance. The gene for neomycin phosphotransferase II (nptII) was used as the selectable marker gene. The explants were cocultivated for 2 days with recombinant Agrobacteria and then submitted to selection on NN69 medium containing 100 mg/l kanamycin. Successful regeneration and conversion of transgenic plantlets were obtained. Stable integration of foreign DNA was confirmed by PCR and Southern blot analyses, and protein expression was detected by Western blot. The regenerated transgenic plants were adapted to the greenhouse and showed no evidence of phenotypical alterations. The foreign genes introduced into the transformed plants did not effect the expected improvement in fungal disease resistance under field conditions for the major pests Uncinula necator and Plasmopara viticola.