Despite antithrombotic prophylaxis, deep vein thrombosis (DVT) remains a frequent complication following major hip surgery. Most of the postoperative DVTs are asymptomatic but may result in fatal pulmonary embolism. Thus, detection of these events remains a clinical challenge. The present study evaluated prospectively the clinical usefulness of a systematic screening for proximal DVT in 173 consecutive patients undergoing major hip surgery and given systematic antithrombotic prophylaxis. On the 12th postoperative day, real-time B-mode ultrasonography of lower limbs veins detected 12 patients (7%) with proximal DVT. None of the individual or surgical characteristics of the patients could help to predict postoperative DVT. Because the sensitivity of ultrasonography for diagnosing DVT in asymptomatic patients may be low and because we did not screen for distal DVT, it was speculated that up to half proximal DVT and up to 75% of all DVT might have been missed by the screening. Therefore, low-dose oral anticoagulation with an INR 1.5-2.0 might be the most cost-effective modality in the postoperative period after the initial perioperative prophylaxis with low-dose heparin, low-molecular-weight heparins or intermittent pneumatic compression boots. Oral anticoagulant treatment might be continued for a total duration of 6 weeks, thereby also providing efficient therapy of undiagnosed distal DVT and prolonged for 3 months in patients with proximal DVT proven by systematic ultrasonographic screening at the time of discharge. The benefit-to-risk ratio of this management strategy deserves further evaluation in a specially designed, prospective trial.