Utilization of transgenic trees as phytoremediation is considered to be one of the cost-effective ways for successive degradation of chlorinated aromatic compounds which are resistant to degradation for decades. In biological degradation pathway of these compounds, chlorocatechols are key intermediates. A bacterial gene cbnA encoding chlorocatechol dioxigenase from Ralstonia eutropha NH9, catalyzes important step for degradation of chlorocatechols and produce toxically reduced 2-chloromuconate. We introduced cbnA gene under the control of CaMV 35S promoter to hybrid poplar by Agrobacterium mediated transformation. Twenty five transgenic lines were isolated and their growth were normal. Accumulation of CbnA translation was visualized by Western blotting. When poplar transgenic calli was incubated in the presence of 3- chlorocatechol, increase of a degradation product*2-chloromuconate peak signal was observed in parallel with reduced peak of the substrate. These results indicated that cbnA was efficiently expressed in the transgenic poplar despite high GC content of cbnA (65%).