About every second decision of a medical doctor concerns drug therapy. On the basis of a representative Norwegian study, which analyzed fatal drug reactions in stationary patients of internal medicine wards by autopsy and plasma drug concentrations, in Germany 58,000 fatalities are occurring in this patient population. The treating physicians classified only 6% of drug induced fatalities as such. Therefore, the risk of drug therapy is grossly underestimated. In half of the cases medication errors were causative and therefore these could potentially all be avoided. In addition to improved pre- and postgraduate education in clinical pharmacology the use of computer-based expert systems would be a decisive step to optimize drug therapy.