We investigated an effect of difference in extremities of DNA on its adsorption onto chemically modified cover glass slips. Two kinds of DNA were used. These are lambda-DNA and lambda-DNA treated with T4 DNA polymerase, which have protruding ends and blunt ends, respectively. The glass substrate surfaces were silanized with 3-aminopropyltrimethoxysilane (APS) or octadecyltrimethoxysilane (OTS). Both DNA molecules were adsorbed on the APS-treated surface due to electrostatic interaction between the positively charged ammonium groups and the negatively charged phosphate groups along the DNA chains, while only untreated lambda-DNA was adsorbed on the OTS-treated surface. The latter result is attributable to hydrophobic interaction between the protruding ends and the OTS-treated surface.