Hydroxyapatite (HA) was coated onto stainless steel (SUS316L) substrates using radio frequency sputtering, and the as-sputtered films were re-crystallized using a low temperature hydrothermal treatment. In order to improve the antithrombogenicity of the HA film, albumin and streptokinase were adsorbed onto the HA film. The amount of adsorbed albumin on the HA film increased from 56 +/- 13 mg/m(2) to 104 +/- 20 mg/m(2) after a 24-h hydrothermal treatment, while the amount of adsorbed streptokinase on the HA film also increased from 4 +/- 2 mg/m(2) to 85 +/- 37 mg/m(2). In the release test, the amount of the albumin and streptokinase released from the HA film increased with incubation time. The 24 h hydrothermally treated HA film with adsorbed streptokinase showed the smallest amount of streptokinase release in all samples. For evaluating the antithrombogenicity of the HA film, clot formation on the HA film was observed using sheep whole blood. Our results indicate that the albumin or streptokinase adsorbed 24 h hydrothermally treated HA films had better antithrombogenicity than the non-coated substrate and the non-adsorbed HA film. (C) 2008 Elsevier B.V. All rights reserved.