This Letter reports the immobilization of DNA onto a solid support by electrostatic interaction with a polycation poly(allylamine hydrochloride) (PAH). The films were analyzed by U-V-vis spectroscopy. The significant observation is that single stranded DNA gets immobilized on the PAH backbone of Layer-by-Layer (LbL) films when the films are fabricated above the melting temperature of DNA. Singly stranded DNA immobilized in the LbL films is not restored into double stranded DNA at room temperature. (C) 2007 Elsevier B.V. All rights reserved.