The fabrication of functionalized surfaces on polymeric substrates is of importance in chemistry, biology, physics, and material science. Examples of functional surfaces are micro/nano periodic arrays that can be fabricated using different methods. However, many of these techniques require several fabrication steps. In this communication, we report the fabrication of advanced architectures in poly(methylmethacrylate)-polystyrene (PMMA-PS) copolymers using direct laser interference patterning. Because of the mixed optical properties of the copolymers, a different type of periodic architectures could be fabricated when compared with traditional pure polymers. This new type of periodic structures results from the local swelling of the copolymer due to the formation of gaseous products induced by the laser radiation. Additionally, relatively low laser fluences are necessary to initiate the ablation process of the copolymers. POLYM. ENG. SCI., 48:23672372, 2008. (C) 2008 Society of Plastics Engineers