The efficient application of a marketed psychotropic drug to mentally ill persons in practice implies ethical problems. The basic ethical issue is to find an optimum of the relationship between the benefits and risks of a medication with regard to major ethical principles. The therapeutic application of psychotropic drugs raises two major questions of ethical significance: (i) is the medication necessary, or do other likewise effective treatments exist with fewer side-effects? (ii) when and about what must the patient be informed before starting a proposed drug treatment? Answers relate different issues of short-term and of long-term medication to ethical principles. An ethical in-depth analysis of the conflict between the principles of beneficence for the individual and of justice for the common welfare is exemplified by a case history of recurrence preventing long-term treatment with neuroleptics as well as by the application of antidementive drugs.