Hydroxyapatite (HAP) and carbonate-hydroxy apatite (CAP5 and CAP15) were synthesized under the flow of N-2 containing 0%, 5%, or 15% CO2 by wet chemical method, and subsequently calcined at 105-700degreesC. Infrared analysis showed that carbonate ions substituted PO43- and OH- sites. The clotting characteristics for the fresh mixed plasma contacted with the samples indicated that CAP had better blood compatibility than HAP. The protein adsorption activity was evaluated by contacting with the model saline containing bovine serum albumin (BSA) and beta2-microgloburin (beta-MG). CAP15 calcined below 600degreesC adsorbed the lowest fraction of BSA (9%) whereas it adsorbed the highest fraction of beta(2)-MG (47%). It was concluded that the selective adsorption activity against beta(2)-MG was related to the carbonate ions incorporated in hydroxyapatite.