A patent foramen ovale (PFO) is a frequent remnant of embryological development with clinical importance in thromboembolism, paradoxical embolism, stroke, platypnea-orthodeoxia, decompression sickness, and migraine headache. The proposed mechanisms of stroke with PFO include paradoxical embolization, in situ thrombosis within the canal of the PFO, associated atrial arrhythmias, and concomitant hypercoagulable states. Prospective trials using aspirin treatment to reduce recurrent stroke showed a significant recurrence of neurologic events in patients with a PFO and atrial septal aneurysm. Use of warfarin anticoagulation does not further reduce recurrent stroke rates compared with antiplatelet therapy. Both surgical and catheter-based modes of closure have been shown to decrease the rate of subsequent embolic events substantially. Successful closure, defined by transesophageal echocardiography, appears to predict freedom from subsequent embolic events. To our knowledge, no randomized trials comparing anticoagulation with surgical or catheter-based closure have been performed.