A novel acridine derivative (1) connected with a disulfide bond through a long methylene spacer has been synthesized, and its interactions with DNA in solutions and at a self-assembled monolayer surface on gold have been studied. Spectroscopic and thermal data indicated that 1 intercalated successfully to DNA in buffer solutions. The mixed monolayers of 1 and 2, which has a similar molecular structure to that of 1 except for the lack of the acridine moiety, on gold substrates were then prepared. When DNA binding properties onto these monolayers were examined by means of a quartz crystal microbalance, there was a monolayer composition (mole fraction of 1 in the mixed monolayer, 0.04) at which the most effective binding of DNA took place. The interaction of this DNA-immobilized monolayer with polylysines (D, L) was examined by comparing circular dichroism spectra before and after binding of polylysines, and such a two-dimensionally immobilized DNA was found to have an ability to bind poly-L-lysine predominately.