The post thrombotic syndrome (PTS) represents sequelae of prior ipsilateral deep venous thrombosis (DVT) [1]. PTS is a form of chronic venous insufficiency (CVI) and is caused by venous hypertension that is provoked by either residual venous obstruction or valvular damage or both. PTS develops in 20–50% of patients with prior proximal DVT [2]. Usual symptoms and signs include leg pain, edema, heaviness and pruritus, all of which are exacerbated by standing. Skin changes range from mild hyperpigmentation to venous ulceration, which is the most burdensome consequence of PTS [3]. Although PTS itself is not a widely recognized condition, it can have a comparable impact on patient quality of life to other chronic illnesses such as heart failure and diabetes mellitus [4–6]. Patients with venous ulcers can have significant disability, leading to time off work, lost productivity and mental health challenges [6, 7]. This chapter summarizes risk factors, diagnosis, prevention, treatment options, and future directions for PTS research.