A prophylactic check for any dental problems should be conducted on patients who suffer from leukaemia before beginning chemotherapy. Bacteraemia caused by oral micro flora may be very dangerous for patients with haematological malignancies. However, it should be noted that the prophylactic process itself might bring about life-threatening complications if there is only a short interval between dental treatment and the beginning of chemotherapy or if the dental treatment is too aggressive.We present a case where this prophylactic procedure produced life-threatening complications for a patient with acute myeloid leukemia. Schlagwörter: Life-threatening complications, AML, dental treatment