In potato, proteinase inhibitor II proteins are encoded by a family of about 10 memmers. They are expressed developmentally in tubers and are induced in leaves upon attacks by insects or mechanical wounding. In order to elucidate the mechanisms of their differential expressions, an inhibitor II gene present in a 13.5 kb EcoRI fragment was isolated from a EcoRI-partial genomic library and characterized. The nucleotide sequence revealed that the gene is complete and encodes an open reading frame of 146 amino acids which is interrupted by an intervening sequence of 113 bp, situated within the codon of amino acid 18. In addition to a promoter element, TATAAA, a sequence resembling a putative regulatory element involved in its wound induction, GCACATCTT, was found at the 5’ flanking region. In order to investigate the mode of expression of this inhibitor II gene, chimeric genes between the inhibitor II gene and bacterial chloramphenicol acetyltransferase (CAT) and β-glucuronidase (GUS) genes were constructed in a binary vector derived from Ti-plasmid of Agrobacterium tumefaciens. Studies of plant transformation will shed light on the mechanism by which this inhibitor II gene is regulated, that is whether this gene is developmentally controlled or induced by environmental conditions or activated under both conditions.