The objective of the investigation was to study how different surface cleaning procedures affect the subsequent adsorption of bovine serum albumin (BSA) on silica. Ellipsometry was used to monitor the adsorbed amount and thickness of the protein films in situ at physiological buffer conditions. Plasma treatment was found to effectively reduce the amount of BSA on silica and on surfaces cleaned with hydrogen peroxide solutions (RCA method) adsorption was essentially absent. On clean silica surfaces the ellipsometric data furthermore suggest that a depletion zone is present at the surface where the BSA concentration is lower than in the bulk solution. Additional experiments showed that calcium did not promote the adsorption of BSA and that the adsorption of human serum albumin (HSA) is essentially absent on clean silica surfaces in agreement with the results obtained for BSA. The presented work contributes to the general understanding of protein adsorption as well as provides information on how to control serum albumin adsorption on silica based biomedical devices.