Current options of secondary prevention of thromboembolism in patent foramen ovale (PFO) are: 1. antiplatelet therapy, 2. anticoagulant therapy, 3. percutaneous transcatheter closure, 4. surgical closure. The optimal preventive strategy of recurrent paradoxical embolism in patients with PFO is not currently known, because it has not been published until now in any randomized study comparing pharmacotherapy with transcatheter closure. The best secondary prophylaxis will probably not be established during the next five years. The indications for transcatheter PFO closure in patients after stroke or transient ischemic attack or peripheral embolism are: proved paradoxical embolism via PFO, very probable paradoxical embolism via PFO (cryptogenic embolic event without any other risk factors in younger patients with proved right-to-left shunt), concomittant atrial septal aneurysm, recurrent event inspite of pharmacotherapy, women before planned pregnancy. The PFO closure is preferred predominantly in younger patients (below 50 - 55 years). There exists assumption, that transcatheter closure offers in comparison with pharmacotherapy greater benefit also in the other groups of high-risk patients: large PFO, significant right-to-left shunt, permanent presence of the shunt even without Valsalva manoeuvre, highly mobile atrial septum.