External compression of the left iliac vein is a common finding in the general population. It may predispose patients to the development of deep vein thrombosis (DVT) of the left leg and may also lead to a more complicated course than in other types of DVT. This entity has been well-described by other authors. External compression of the left iliac vein should be suspected in cases of complicated DVT or in cases of DVT with no predisposing factors. We describe a case of May-Thurner syndrome that involved a complicated treatment course, and a review of current options for diagnosis and therapy.