A transformation system for Chinese cabbage protoplasts was developed using Agrobacterium tumefaciens strain LBA4404 (harbouring the plasmid pBinΩSCK and the plasmid pMOG 411 respectively). The plasmid pBinΩSCK contains a 415 bp insert derived from the Cowpea trypsin proteinase inhibitor gene and The plasmid pMOG 411 contains a 870 bp fragment which codes an anti-bacterial peptide gene. Freshly isolated protoplasts of Chinese cabbage (Brassica campestris L.ssp.pekinensis) lines were pre-treated at 4 ∘C for 1 h, then incubated at 25 ∘C for 2–3 days in the dark. 3 drops of A. tumefaciens solution in log-phase were added to 10 ml protoplasts and cocultivated for 48 h at 25 ∘C. Some kanamycin-resistant plants and a number of kanamycin-resistant calli were obtained. Southern blot hybridization analysis demonstrated the presence of the CpTI gene and the anti-bacterial peptide gene in the Chinese cabbage genome. Northern blot analysis of the kanamycin-resistant plantlets and calli confirmed the accumulation of the CpTI and the anti-bacterial peptide mRNAs.