A prospective study of thrombo-embolism after total hip replacement in epidural analgesia was carried out in 116 patients, randomly allocated to dextran 70 or low-dose heparin combined with dihydroergotamine (HDHE). Amounts of blood loss and transfused bank blood did not differ significantly between dextran 70 and HDHE prophylaxis. There was a lower incidence of femoral deep vein thromboses in patients given dextran prophylaxis as compared with those on HDHE (P less than 0.05). However, the total frequency of DVT and the frequency of pulmonary embolism did not differ between the two groups. There was no case of fatal pulmonary embolism. The side effects were major bleeding complications in 7 per cent of the HDHE group as compared to none in the dextran group. No anaphylactic reaction was noted from dextran 70 using hapten-dextran prophylaxis.