1. In a prospective controlled trial in patients undergoing hip operations, six out of thirty-three patients receiving prophylactic Dextran 70, and five out of thirty-three patients receiving only dextrose, were shown by ascending phlebography to have ilio-femoral thrombosis. Oedema was the only consistent clinical finding.

2. This study does not therefore support the conclusion of other reports that Dextran 70 is of value in preventing ilio-femoral thrombosis after operations on the hip joint.

3. It is suggested that patients needing operation on the hip joint are especially prone to major vein thrombosis and it may be that higher dosage of Dextran 70 is indicated.

4. This controlled investigation of sixty-six patients, now submitted as a preliminary report, is continuing.