In a prospective randomized study heptest, thrombin-antithrombin complexes (TAT), D-dimer, and t-PA:ag were analysed pre- and postoperatively in 206 consecutive patients undergoing hip arthroplasty during thromboprophylaxis with either a LMW heparin (Enoxaparin) or Dextran 70. Deep vein thrombosis (DVT) developed in 6 of 102 (6%) Enoxaparin and in 21 of 104 (20%) Dextran patients diagnosed by bilateral phelobography. In the Enoxaparin group heptest showed a significant increase from the pre- to the postoperative level opposed to a significant decrease in the Dextran group. Postoperative levels of TAT, D-dimer, and t-PA:ag were significantly increased in both groups, however, TAT was significantly higher in patients in the Dextran group than in the Enoxaparin patients. D-dimer was significantly higher in Dextran patients with DVT postoperatively compared with patients without DVT. No differences concerning TAT or t-PA:ag were observed between patients with and without DVT in any of the groups.