After deep vein thrombosis (DVT) 20-50%, of patients develop post thrombotic syndrome (PTS). Up till now, there is no effective treatment for PTS and prevention is therefore of major importance. Compression therapy after DVT, with elastic compression stockings (ECS), is the only available preventive measure for PTS. However, the usefulness, timing, and duration of compression therapy are matters of debate. The effect of early compression on the long-term development of PTS is still unclear as studies performed so far have conflicting outcomes. The effectiveness of ECS therapy initiated in the sub-acute phase was assessed in three large randomized controlled trials. Kahn et al could not reproduce the large risk reduction found in the trials by Brandjes and Prandoni et al. Also for the optimal duration of ECS therapy, a certain conclusion has yet to be drawn. Therefore identification of patients who most likely will benefit from ECS therapy as well as the optimal ECS treatment strategy remain subjects for further study.