Hydroxyapatite is widely utilized as a component in dental hygiene agents. The ability to adsorb and remove dental plaque adhering to tooth surfaces is recognized as an important property of hydroxyapatite particles. In this study, the adsorptive ability of hydroxyapatite was evaluated based on its adsorptive amount and adsorptive strength. The adsorptive amount was determined by measuring the weight of albumin, dextran and lipids adsorbing to hydroxyapatite. The adsorptive strength was determined by measuring the weights of albumin and dextran remaining adsorbed after rinsing. Similar procedures were performed in control experiments using calcium hydrogen phosphate dihydrate, alumina and sericite. The results showed that the weights of albumin and dextran adsorbed to hydroxyapatite were 1.4 +/- 0.13 and 1.6 +/- 0.30 times higher than that to calcium hydrogen phosphate dihydrate. The weight of lipids adsorbed to hydroxyapatite was much higher than that to alumina and sericite. The percentages of weight loss of albumin and dextran were 2.3 +/- 1.7% and 5.3 +/- 2.0% for hydroxyapatite and 27 +/- 6.8% and 19 +/- 11% for calcium hydrogen phosphate dihydrate after one rinse. It is concluded that hydroxyapatite is a better adsorbent than calcium hydrogen phosphate dihydrate, alumina and sericite with respect to adsorbing albumin, dextran and lipids.