We demonstrate an effective method for DNA immobilization on a hydrophobic glass surface. The new DNA immobilizing technique is extremely simple compared with conventional techniques that require heterobifunctional crosslinking reagent between DNA and substrate surface that are both modified chemically. In the first process, a coverslip was treated with dichlorodimethylsilane resulting in hydrophobic surface. λ DNA molecules were ligated with 3´-terminus disulfide-modified 14 mer oligonucleotides at one cohesive end. After reduction of the disulfide to sulfhydryl (thiol) groups the resulting thiol-modified λ DNA molecules were reacted on silanized coverslip. Fluorescent observation showed that the thiol-modified λ DNA molecules were anchored specifically to the hydrophobic surface at one terminus, although non-specific binding of the DNA molecules was suppressed. It was observed that the one-end-attached DNA molecule was bound firmly to the surface and stretched reversibly in one direction when a d.c. electric field was applied.