Background. Inherited predisposing risk factors for deep venous thrombosis (DVT) have been clearly identified in Caucasians, but there are fewer reports evaluating these factors in the Japanese. This study was undertaken to assess the predisposing risk factors for DVT following elective total hip arthroplasty (THA) in Japanese patients. Methods. We studied 60 patients who underwent THA. The study group consisted of 30 patients who developed DVT diagnosed by duplex sonography examination; the 30 patients who did not develop DVT served as a control group. They were matched in age, sex distribution, diagnosis (osteoarthritis secondary to dysplastic hip), and operation side(s) (bilateral or unilateral). Protein C, protein S, antithrombin III, and plasminogen activities and the plasma homocysteine level were measured. Three polymorphisms were screened for the factor V Leiden polymorphism, the factor II G20210A polymorphism, and the methylene tetrahydrofolate reductase C677T polymorphism. Results. Plasma protein C activity was 82.39% ± 14.24% in the DVT patients and 88.76% ± 23.27% in the controls. Plasma protein C activity was significantly reduced in the study group, whereas other serologic and genetic analyses revealed no significant differences. Conclusions. Three genetic risk factors established in Caucasian patients are not valuable for evaluating DVT risk in Japanese patients. Reduced protein C activity may be a risk factor for DVT after THA.