The binding of anticancer drug dacarbazine (DTIC) to DNA bases in the absence and presence of Au nanoparticles has been explored by electrochemical study. The results indicate that the binding of purines (adenine and guanine) to DTIC is stronger than that of pyrimidines (thymine and cytosine) in the order of A > G > C > T. It was also observed that the presence of gold nanoparticles could facilitate the specific interaction between DTIC with DNA bases. (C) 2004 The Electrochemical Society.