‹Background› Recently, the incidences of pulmonary embolism (PE) and/or deep vein thrombosis (DVT) after orthopedic operation increased in Japan. However the effective prevention methods have not been established yet. To make the effective prevention of PE and/or DVT after total hip arthroplasty (THA), we investigated the time-dependent changes of serum thrombin-antithrombin III complex (TAT) and D-dimer levels after THA. ‹Subjects & Methods› We measured changes of serum TAT, and D-dimer levels (before, on day 1, day 5, week 2 and week 4 after operation). Twenty-six women (mean age 64.5 years old), who had undergone THA for osteoarthritis of the hip joint were enrolled and divided into two groups at random. One group had been intravenously injected with 1,000 units of heparin during THA (IH Group, 14 patients), and the other group had not been injected (NH Group, 12 patients). ‹Results› No patients showed clinical PE and/or, DVT. The levels of TAT and D-dimer in IH group significantly reduced compared with these in NH group on the fifth and first postoperative day, respectively (p < 0.05). There were no severe complications clinically. ‹Conclusion› Our data suggests that intravenous heparin injection during THA might be a potentially effective and safe strategy for prophylaxis of PE after THA.