The adsorption of bovine serum albumin (BSA) was investigated on two metal surfaces, chromium and molybdenum, in pure water and in a phosphate buffer solution (pH 7). Fourier-transform infrared reflection-absorption spectroscopy (FT-IRRAS) and X-ray photoelectron spectroscopy (XPS) were used to characterize the surfaces after immersion times ranging from 2 min to 1 h. In pure water, short times of immersion (a few minutes) resulted in higher BSA adsorption on Cr than on Mo; for longer times (20 min, 1h), the amount of BSA was similar on both surfaces. Changes in the conformation of the BSA molecules when the coverage increases were evidenced by the position and shape of the IR amide band. A more compact structure was observed on chromium. On molybdenum, the amideI/amide II intensity ratio did not change significantly with time or BSA concentration, indicating limited change in the conformation upon adsorption. In a Na2HPO4 + NaH2PO4 buffer solution, both FT-IRRAS and XPS data show that the amount of proteins adsorbed is reduced by a factor of close to three. Competitive adsorption of phosphates and proteins was inferred to explain this phenomenon.