Factor assays of normal human citrated plasma following incubation with the surfaces of synthetic polymeric materials such as polypropylene and propylene-ethylene copolymers, and polyamide compounds were performed in high surface area-plasma volume ratios. Polypropylene and propylene-ethylene copolymers: In the intrinsic pathway, the activity of factor VIII showed a significant pattern of enhancement, but no alteration in the activities of factors IX, XI and XII was observed. On the other hand, in the extrinsic pathway, the activity of factor II seemed to be potentiated, but the activities of factors V and X seemed to be reduced, and the activity of factor VII showed significant pattern of reduction, which was consistent with propylene structure. Enhancement in the activity of coagulation factor might be caused by feed back mechanism among coagulation factors and by cleavage of molecules of coagulation factors. Polyamide compounds: In the intrinsic pathway, the activities of coagulation factors were not influenced. Even in the extrinsic pathway, only the activities of coagulation factors I and II were significantly reduced and those of the others were not depressed.

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