Recent trials on secondary prophylaxis after venous thromboembolism (VTE) have provided a wealth of data on the risk factors for recurrence and, to some extent, also for bleeding. Some of the results are consistent across the studies, but there are also conflicting data. Certain risk factors, such as pulmonary embolism versus deep vein thrombosis or presence of cardiolipin antibodies, have a more pronounced influence on the risk early in the course of disease. Others, such as hereditary throm- bophilic defects, seem to gain importance over many years of follow-up. Therefore, it can be difficult to make decisions on an individual patient basis. In this article,data from important and illustrative trials have been extracted and compared and controversies highlighted. The conclusions drawn should help clinicians make balanced decisions on the optimal duration of anticoagulation after an episode of VTE.