Summary Venous thromboembolism (VTE) is most preventable and unacceptably over 25,000 people die of VTE annually in England. The scale of VTE mortality prompted the UK Department of Health to charge the National Institute for Health and Clinical Excellence (NICE) with the task of developing a national guideline for reducing the risk of VTE in high risk surgical patients. The VTE guideline development group was tasked to review the effectiveness of methods of prophylaxis in patients undergoing high risk surgical procedures and make recommendations on the most clinically and cost effective measure to reduce VTE in such populations. Systematic reviews and meta-analyses of published randomized trials of mechanical and pharmacological prophylaxis for VTE, as determined by objective methods of screening were primarily considered. Other inclusion criteria comprised of randomised clinical trials of specific types of major surgery deemed to be associated with high incidence of VTE. The studies compared a single method of prophylaxis with nil or another strategy. Clinical trials of mechanical devices used as an adjunct to pharmacological methods were also scrutinised. All prophylactic strategies reduce the risk of developing post operative DVT compared to no prophylaxis. However, all pharmacological interventions are associated with an increased risk of bleeding. As mechanical methods demonstrate similar efficacy and risk reduction to pharmacological methods and without bleeding complications, they are recommended as first choice of venous thromboprophylaxis. It is also acknowledged that adding a mechanical device to low molecular weight heparin or unfractionated heparin in some high risk patients reduces the risk of postoperative DVT more significantly.