An efficient transformation system was developed for Centaurea montana by co-cultivation of leaf explants with Agrobacterium tumefaciens strain AGL1 that contained a plasmid harboring the isopentenyl transferase gene under the control of the developmentally regulated Atmyb32 promoter of Arabidopsis thaliana and the gene encoding for hygromycin resistance under the control of the Cauliflower Mosaic Virus 35S (CaMV35S) promoter. A total of 990 explants were infected with Agrobacterium, and 18 shoots were regenerated resulting in an overall transformation efficiency of 1.8%. Molecular analyses, including PCR, Southern blotting and RT-PCR, were performed on T-0 and T-1 plants to confirm chromosomal integration and expression of the transgene in the phenotypically normal transformed plants. Transformation of C. montana was also performed using A. tumefaciens supervirulent strain EHA105 harboring the beta-glucuronidase (GUS) reporter gene. Expression of the GUS gene in the putative transgenics was confirmed using a histochemical GUS assay.