Historically medical decision support systems (DSS) emerged from medical biometry and medical informatics. Both disciplines haved pursued different approaches over decades, with only minor exchange or mutual fertilization. Therefore, it is timely to work towards exchange of concepts and possible integration of methods between these and other newly delevoping disciplines such as Artificial Neural Networks (ANN). It is the purpose of this abstract to identify underlying assumptions of different approaches and how they relate to present developments in health care. Among these developments the intension to base decisions on as much information as possible and to improve quality of care are most closely related to the targets of DSS.