In a prospective, double-blind, controlled study, we compared the antithrombotic efficacy of low-dose heparin with dihydroergotamine (A), low-molecular-weight heparin with dihydroergotamine (B), and placebo (C). Two hundred and thirteen patients surgically treated for fractures of the hip were randomly divided into three groups. One hundred and sixty-one patients were analyzed. All thrombi were verified by ascending phlebography. Nine patients died within 1 month after operation. A and B proved to be equally safe but failed to provide any protection against deep-vein thrombosis, although B showed a tendency to reduce the incidence. Mortality within 1 month of operation was unaffected by the type of prophylaxis.