Deep vein thrombosis (DVT) and pulmonary embolism (PE) are common and serious post-operative complications. The risk depends on age, general condition, length of operation and type of surgery. Properly used prophylactic therapy with unfractionated heparin, low molecular weight heparin or two-step warfarin can reduce post-operative deaths from PE by 70% and reduce DVT by 50-80% without increasing the risk of serious postoperative bleeding. This review article summarizes the outcome of multiple controlled trials of surgical thromboprophylaxis with various medications.