The religious community of Jehovah's Witnesses holds that blood transfusion is against God's law. Therefore, surgical treatment of Jehovah's Witnesses is a great challenge for every surgeon, especially for cardiac surgeons because blood transfusion is frequently needed during such operations. In this study we summarize the experience with Jehovah's Witnesses who have undergone open-heart surgery in Debrecen from 1989 to 1999 due to various cardiac diseases. Applying a complex surgical procedure developed by the authors to minimize blood loss during operation, preserved blood products were omitted. Three patients out of twenty-four died during the postoperative period. The twenty-one longtime survivors showed significant improvement in their clinical stage during the mean follow up of 37.6 months. More and more operations are done successfully without blood or preserved blood products worldwide, so it could be said that nowadays surgical treatment of Jehovah's Witnesses has a lower risk than before.