The Rendu-Osler-Weber disease is due to an autosomal dominant disease with multiple telangiectasia in skin and mucosa. Recurrent bleeding of the nose is due to telangiectasia of the nasal mucosa. Haemorrhage of the oral mucosa also occurs. Extensive arteriovenous malformations can be present in lungs, liver and brain. Treatment of bleedings in the oral mucosa is easily possible by means of coagulation. Patients with pulmonary arteriovenous malformations should receive prophylactic antibiotic treatment before extractions, removal of third molars and subgingival curettage.