More and more patients receiving anticoagulant therapy or other drugs modifying the coagulation mechanism require dental or oral surgical treatment nowadays. The reason is that in Hungary the various forms of thrombosis are on the first place of morbidity and mortality lists. More than 50 per cent of all the mortality is due to thromboembolism. In view of all this it is not surprising that in the past years the indications, application and dosage of anticoagulant and platelet aggregation inhibitor drugs have changed. Decades-old principles have been modified. It is important for dentists and oral surgeons to know the risk of interventions in patients receiving anticoagulant or platelet inhibitory therapy.