In this paper, the electrochemical behavior of the CTZAMB-Cu(II) complex with DNA has been investigated in potassium hydrogen-phthalate buffer solution (pH 2.5). In the absence of DNA, there was a sharp reduction peak in the single sweep polarogram due to the presence of CTZAMB-Cu(II), while in the presence of DNA this peak decreased in a quantitative fashion. This decrease in peak current is due to the formation of the CTZAMB-Cu(II)-DNA complex. Under the optimum conditions, the decrease of peak current is linear with DNA concentration in the range from 3.0 x 10(-7) to 7.0 x 10(-6) g ml(-1), and the detection limit is 1.0 x 10(-7) g ml(-1). This new method exhibits a good recovery and sensitivity, which could be applied to the determination of DNA in real samples. The mechanism of the interaction of DNA and CTZAMB-Cu(II) is also discussed. (c) 2005 Elsevier B.V. All rights reserved.