Patients with inflammatory bowel disease (IBD) are known to have an increased propensity for thromboembolic events. Like any patient with a high risk of event recurrence, most of these patients can be managed successfully with long-term warfarin therapy. We present the case of a 66-year-old woman with Crohn's disease who, despite careful attention to the management of her international normalized ratio, developed a new deep vein thrombosis and required inferior vena cava filter placement in addition to ongoing warfarin therapy to prevent recurrent pulmonary emboli. This report serves as a reminder to physicians to have a low threshold for diagnosing thromboembolic events in patients with IBD, even if they are presumed to be adequately anticoagulated. Known and theoretical contributing factors to this increased clotting tendency are also reviewed. © Postgraduate Medicine.