The risk of endocarditis developing as the consequence of a bacteremia caused by a health care procedure in a patient with a predisposing heart disease is small. The administration of antibiotics before such a procedure is thought to reduce this risk still further. However, the protective effect of this preventive measure has never been demonstrated in a prospective randomized study. With certainty it can be said though, that it is not 100% efficacious and reports on prophylaxis failure have appeared ever since the introduction of this preventive measure. The revised guidelines are as far as possible based on published data. Where data are lacking, experts opinion was followed. The guidelines are not exhaustive and do not cover each and every circumstance in which prophylaxis could be warrantable. The purpose of the guidelines is to give the clinician something to go by in the most frequently occurring health care procedures. Not everyone will agree with the choices made by the commission in areas where data are lacking. In these areas, local directives may differ from the published directives. For a made to order advice on prophylaxis one should turn to an expert on endocarditis.