The ozone etching of a commercial poly(styrene)/poly(isoprene) (PS/PI) block copolymer (Kraton D 1117) was studied by atomic force microscopy. The copolymer contains 17% PS and forms a cylindrical phase in the melt. The copolymer dewetted when spin coated onto a silicon wafer but the film was stable on a grown silicon oxide layer. The structure of the stripe pattern formed was examined on substrates with different oxide layer thicknesses (surface energies). Finally etching by ozone was investigated. For low ozone doses, no degradation of polymer was observable. Extended ozone treatment resulted in more obvious degradation, but the etching was non-selective. (C) 2003 Elsevier Science Ltd. All rights reserved.