To report the risk of fatal atrial migration with the Tempofilter.Among temporary filters, the high safety profile Tempofilter has been marketed as offering protection for up to 6 weeks. We implanted about 60 Tempofilters to prevent pulmonary embolism. The main indications were temporary thromboembolic risk, recurrent pulmonary embolism, and contraindication to or failure of anticoagulant therapy. Follow-up was performed regularly by plain abdominal film and Doppler ultrasound. Filters were removed about 4 weeks after placement.We encountered three cases (5%) of atrial migration and one case of 5-cm cephalad displacement of the filter. Of the three patients with atrial migration, two died within 3 days of implantation, one from a massive pulmonary embolism and the other with cardiac tamponade. One patient did not show any serious complications.The Tempofilter may actively migrate cranially and become dangerous in the case of migration within the heart.