Implantable biomaterials, such as Ti-6Al-4V alloy, are designed to replace a part of the human body and/or its associated functions. This system, containing the alloy onto which the osteoprogenitor cells are deposited, is formed through the grafting of linear RGD (Arginine-Glycine-Aspartic acid) peptides. Our preliminary work demonstrated that the bonding of the fibronectin cell attachment peptide RGD to a metallic surface is extremely successful in promoting the adhesion and the proliferation of osteoprogenitor cells. However, a fuller understanding of the relationship between surface coverage and the contribution of each layer is required, in order to optimize the efficiency of the RGD-modified surface through optimal RGD bonding. We have used the TOF-S-SIMS analysis of this new surface, previously studied by XPS, to follow each modification level. Functional groups for peptide immobilization are required at the metallic surface, and their presence has been identified by mass spectra. A relative quantification of immobilized RGD peptides is obtained by TOF-S-SIMS analysis. Molecular ion imaging informs us of the surface evolution throughout the modification process and offers a description of each group. A comparative analysis of the spectra has permitted us to correlate the presence of these species on the surface with their bioactivities. (c) 2006 Elsevier B.V. All rights reserved.