Monolayer films of n-octadecylamine (ODA) on the subphase containing oligomeric DNA and CdCl2 were transferred onto substrates by the Langmuir-Blodgett method at different surface pressures. After exposing these monolayer films to H2S gas, CdS nanoparticles were formed on oligomeric DNA template. Transmission electron microscopy (TEM) observations indicate that on the film transferred at low surface pressure, CdS nanoparticles are arranged in string-of-beads manner, and on that deposited at high surface pressure, CdS nanoparticles are observed as isolated dots. (C) 2002 Published by Elsevier Science B.V.