A prospective randomised trial was carried comparing the use of Enoxaparin with intermittent pneumatic calf compression garments for thromboprophylaxis in total hip replacement. Fifty consecutive patients were studied and randomised to evaluate these two methods. There were 2 deep vein thromboses, one in each group, and no cases of pulmonary embolism. The operative field was judged to be drier in the compression group, but the mean fall in the postoperative haemoglobin level was the same in each. In the peroperative period, 6 patients in the Enoxaparin group needed 2 units of blood and one 3 units. In the compression group, 3 patients needed transfusions of 2 units. Intermittent calf compression has fewer problems than the use of Enoxaparin and has no contraindications.