In medicine, the “available evidence” is the sum of the relevant knowledge that can be used to reach valid conclusions and produce the most reliable recommendations possible at a given point in time. Therefore, it is important to remember that scientific evidence cannot provide absolute truth; it can change with time as new findings and, thus, new evidence arises. The American College of Chest Physicians (ACCP) guidelines for the prevention of venous thromboembolism (VTE) reflect the available evidence on postoperative VTE prophylaxis, gained through a systematic review of the literature. However, the methodology used, which is mostly based on the incidence of asymptomatic thrombosis, may not be the most appropriate. Surrogate venographic endpoints should gradually be replaced by clinical endpoints such as symptomatic VTE, death-related events, and bleeding complications. For now, European orthopaedists should combinethe ACCP guideline recommendations with those of national guidelines, as well as newer evidence, specific patient factors, and their own clinical judgment. Adv Orthop 2009;1(2):50–57.