Biodegradable poly(3-hydroxyundecenoate) (PHU) films on silicon wafers were crosslinked with UV light under patterned masks. The films were eked most efficiently whets irradiated in the presence of diphenyl(2,4,6-trimethylbenzoylphosphane oxide)as the initiator. Crosslinked patterns were developed, with. depolymerase solution because crosslinked teas degraded much more slowly than natural PHU. Patterned images with thicknesses of as low as 2.5 mum were obtained showing the potential application of PHU in microlithography as a photosensitive material, which is friendly to the environment.