Deep venous thrombosis (DVT) and pulmonary embolism (PE) are potentially life-threatening complications associated with orthopaedic surgery. The choice of an optimal thromboprophylaxis regimen requires full understanding of the efficacy and safety profiles associated with distinct treatments. Low-molecular-weight heparins (LMWHs) are the drugs of choice for thromboprophylaxis in orthopaedic surgery. However, there is concern regarding the timing of LMWH prophylaxis initiation. Among the LMWH molecules, bemiparin has interesting pharmacological properties: the lowest molecular weight, the longest half-life and the highest anti-FXa/anti-FIIa activity ratio. The safety and efficacy of bemiparin administered 6 hours after surgery has been demonstrated in several orthopaedic settings (including major orthopaedic surgery, knee arthroscopy, lower limb trauma and spinal surgery) and during prolonged prophylaxis after major orthopaedic surgery. Another factor to consider in relation to thromboprophylaxis during orthopaedic surgery is the cost effectiveness of bemiparin. The 91st meeting of the Italian Society of Orthopaedics and Traumatology (SIOT), held in Rome, Italy, on 12-16 November 2006, provided an exciting opportunity to present new and interesting evidence, including the latest advances in thromboprophylaxis in orthopaedic surgery. Of particular interest were the issues debated during the Sigma Tau/ROVI Satellite Symposium, which focused on the optimal timing strategy for initiating thromboprophylaxis in patients undergoing orthopaedic surgery. This article highlights presentations given during that symposium.