A thaumatin II cDNA (thau II) driven by the CaMV 35S promoter was introduced into tomato line YALF via Agrobacterium-mediated transformation. The pBI121-based binary vector for expression of this gene was constructed using a coding sequence cloned at Leiden University. Twenty-three transformants obtained on the selective media with kanamycin were tested for the presence of the neomycin phosphotransferase (nptII) and thaumatin II (thauII) genes. The nptII gene was detected in all kanamycin-resistant plants but among them only 16 contained thauII. Transformation frequency was 9.4%. Accumulation of the foreign protein in leaves and fruits of transgenic plants was confirmed by Western blotting. The foreign gene expression in the fruits was detected organoleptically. Greenhouse testing confirmed enhanced resistance against Phytophtora infestans for two thaumatin-producing tomato lines. Inheritance of transferred genes in the T1generation and vector design for cell compartmentalization of foreign protein expression will be discussed.