Dihydro-ergotaraine (DHE) appears to be synergistic with small doses of hepari when used to prevent VT after general surgery. However, doubt remains whether DHEhas this effect in patients with elective hip replacement (THR). We have therefore compared the results of VT prophylaxis using sub-cutaneous (sc) low-dose heparinalone or sc heparin plus sc DHE in a double-blind, randomised, study of 126 patientshaving elective THR, 98 at centre (1)and 28 at centre (2).All received 5000 iu sodium heparin, hourly for 7 days, starting 2 hours before surgery at centre (1), or immediately after surgery at centre (2). Patients alsoreceived a separate 0.5 ml (0.5 mg) DHEorplacebo injection each time they receivedheparin. Patients had bilateral ascendingvenography on the 7th postoperativeday, and venograms were read before the treatment code was broken.These results do not support the presence of synergism between heparin and DHE in this situation.