A 42-year-old patient with cardiac problems had periodontal disease. The required periodontal treatment was only carried out after a period of 6 months. During this time, the patient was at risk of endocarditis due to a bacteraemia, a problem which was not recognized by any of the oral healthcare providers. When treating a patient who is at risk of developing endocarditis, the guidelines of the Dutch Heart Foundation (Nederlandse Hartstichting) must be observed. Deviation from the guidelines is only permissible under appropriate conditions. If treatment is being carried out by a team, then there is not only a question of shared responsibility, but also of shared liability. Adequate communication and record-keeping are vital in cases of patients who are medically compromised.