In the electroanalytical fields, carbon nanotubes (CNTs) have been usually utilized to modify the electrodes to enhance the relevant detection sensitivity because of their unique physical and chemical properties. In this research, novel nanocomposites of beta-cyclodextrin and multi-wall CNT (MWCNTs) have been prepared and deposited on the glassy carbon electrodes to form the beta-CyDex/MWNT modified electrodes. These novel modified electrodes offer a new strategy for the simultaneous determination of guanine (G), adenine (A) and thymine (T). Well separated voltammetric peaks are obtained between G and A (330 mV), A and T (170 mV) present in the analyte mixture. The detection limits of A, T and G for individual analysis can be calculated to be 0.75, 6.768 and 33.67 +/- 7.8% nmol L(-1), respectively. The functional properties of the composite films from differential pulse voltammetry (DPV) show that the beta-CyDex/MWNT nanocomposites modified electrodes are quite sensitive and could be readily applied in biosensor devices. (C) 2009 Elsevier B.V. All rights reserved.