Titanium (Ti) is very effective as a dental implant material owing to its low toxicity and high biocompatibility. I carried out in vitro experiments on the adsorption of salivary proteins and serum proteins to Ti to better understand how this material reacts in the oral cavity. I found that when Ti that had adsorbed serum proteins was exposed to salivary proteins, there was an exchange of the proteins on the Ti surface. The same thing happened when Ti that had adsorbed salivary proteins was exposed to serum proteins. These results suggest that both human salivary proteins and serum proteins adsorb to Ti with different affinity, and that protein already adsorbed to Ti might mask binding sites for other proteins.