The post-thrombotic syndrome (PTS) is a long-term complication of deep venous thrombosis (DVT) that is characterized by chronic, persistent pain, swelling and other signs in the affected limb. PTS is common, burdensome and costly. It is likely to increase in prevalence, since despite widespread use of and improvements in the efficacy of thromboprophylaxis, the incidence of DVT has not decreased over time. About 20-50% of patients develop PTS within 1-2 years of symptomatic DVT, and severe PTS, which can include venous ulcers, occurs in 5-10% of cases. Although there is no gold standard for the diagnosis of PTS, the presence of typical clinical features in a patient with previous DVT provides strong supporting evidence. Objective evidence of venous valvular incompetence helps to confirm the diagnosis in symptomatic patients. Preventing ipsilateral recurrence of DVT, by ensuring an adequate duration and intensity of anticoagulation for the initial DVT and by prescribing situational thromboprophylaxis after discontinuation of oral anticoagulants, is likely to reduce the risk of developing PTS. There is no proven role for thrombolysis of the initial DVT to prevent PTS. Daily use of graduated compression stockings after DVT may reduce the risk of PTS, and may prevent worsening of established PTS. Pending the results of ongoing studies, stockings are recommended in patients with persistent symptoms or swelling after DVT. Future research should focus on standardizing criteria for PTS diagnosis, identification of DVT patients at high risk for PTS, and rigorously evaluating the effectiveness of stockings, thrombolysis, and venoactive drugs in preventing or treating PTS.