SU-8 photoresist polymer is widely used in the fabrication of microdevices. However, for biological applications, the problem of efficiently modifying SU-8 surfaces without perturbing roughness has not been successfully resolved. We present UV/ozone (UVO) surface pre-treatment as an effective method to increase the hydrophilicity of SU-8 films without affecting surface roughness, thus improving specific covalent binding of bio-molecules. We demonstrate that 30 s UVO treatment suffices to create carboxyl groups at the surface that can then be used for high density binding of molecules via amide bond formation. We further demonstrate that a two-step surface modification where the surface is first protected with an ethylene glycol monolayer leads to an increase in binding specificity. Finally, to illustrate the con-trolled binding and accessibility of immobilized molecules, we show three cycles of reversible interactions between anti-tamra antibody and tamra-cadaverine immobilized on the surface of SU-8.