Pathogenesis-related protein-1a (PR-1a) is strongly induced in tobacco plants by pathogen attack, exogenous salicylic acid (SA) application and by other developmental processes. In order to develop a rapid screening system for the selection of plant defenseinducing compounds originated from various sources,we have transformed tobacco Samsun NN plants with a chimeric construct consisting of GUS (β-glucuronidase).In the T1 generation, three transgenic lines having stable GUS expression were selected for further promoter analysis. Using GUS histochemical assay, we observed strong GUS induction driven by PR-1a promoter in PR1a-GUS transgenic tobacco leaves in response to the exogenous application of SA or benzol (1,2,3) thiadiazole-7-carbothioic acid S-methyl ester (BTH), a SAderivative compound. In addition, GUS expression was maintained locally or systemically in PR1a-GUS transgenic line # 5 (T2 generation) until after 3 days when they were treated with same chemicals. Our results suggested that the PR1a-GUS reporter gene system in tobacco plants may be applicable for the large-scale screening of defense-inducing substances.