To elucidate the effect of DNA base-mismatch on the charge transfer through DNA, we investigated stable structures and electronic properties of double-strand DNA and its base-mismatched ones by semiempirical molecular orbital calculations. Based on these electronic properties, we analyzed the charge transfer by using an I-V simulator based on the Landauer formula. The results indicate that the base-pair mismatches (A-C and G-A) affect the electronic properties around the Fermi level, so that the hole conductivity through double strand DNA is significantly reduced by these mismatches. (c) 2005 Elsevier B.V. All rights reserved.