Electrografting provides a method for the direct (Si-C) covalent functionalization of silicon surfaces. In this work, cathodic electrografting of hexynoic acid to silicon nanowire surfaces and subsequent immobilization of bovine serum albumin (BSA) is demonstrated. Hexynoic acid was cathodically electrografted to dense arrays of silicon nanowires approximately 50-100 nm in diameter and 10 mu m in length. Protein immobilization was achieved via amidization reactions with carboxylic moieties of electrografted hexynoic acids. Results include chronoamperometric data from the electrografting process and verification of attachment using attenuated total reflectance Fourier transform infrared spectroscopy (FTIR) of electrografted hexynoic acid and immobilized BSA. In addition to FTIR analysis, covalently immobilized BSA was verified using fluorescence microscopy and solution-phase fluorescence. (C) 2008 The Electrochemical Society.