Communication: In lithographic techniques for forming nanostructures in surfaces and polymer thin films, the selectivity of the solvent becomes increasingly important as the target dimensions decrease. Polymer-based resist systems are reported that use supercritical (SC) CO2 instead of water-based developers. The Figure shows the SC CO2-developed image of a copolymer of pentafluoropropyl methacrylate and tert-butyl methacrylate.