The authors report the results of a randomised double-blind study comparing the antithrombotic activity of a new anti-platelet drug (Triflusal) with that of acetylsalicylic acid (ASA). 99 patients who underwent hip surgery were included in the study (total hip replacement, osteosynthesis of a pertrochanter fracture or Moore's prosthesis for intracapsular fracture of the femoral neck). Of the 48 patients having received Triflusal, 7 (14.5%) developed deep vein thrombosis as indicated by 125I-fibrinogen isotopic scanning and confirmed by phlebography. Of the 51 patients treated with ASA, 11 (21.6%) presented the same complication as diagnosed by the same techniques. This difference is not statistically significant, considering the number of cases studied. Nevertheless, Triflusal appears to provide prevention of thromboembolic risk to patients who have undergone hip surgery, particularly total hip replacement.