Terminally alkylated heparin was prepared by reducing the terminal end of heparin and subsequent lactone formation, followed by ring-opening reaction with alkylamine. The alkyl groups used include butyl, octyl, lauryl, and stearyl. These alkylated heparins adsorbed on the poly(ethylene terephthalate) film from their respective aqueous solutions. The adsorptivity and its stability in buffer solution, complexation compatibility with antithrombin III (ATIII), were enhanced with larger alkyl-group-derivatized heparins. These were assessed using a confocal laser scanning microscope. The "heparin surfactant" developed here may be used for ensured short-term "system antithrombogenicity" of assembled extracorporeal circulatory devices or circuits.