Psychiatric diagnoses are imprecise and that imprecision flows from current diagnostic criteria. Essentially psychiatric conditions are viewed, reported, and studied from a syndromal perspective. That is, if sufficient signs and symptoms are present, then a specific diagnosis can be made. This relative "softness" contrasts with more pathophysiology-based diagnostic criteria used by our medical-surgical colleagues. As psychiatry and psychiatric nursing move toward a more scientific base for diagnosis, a greater emphasis has been placed on psychobiological dimensions of illness. The most aggressive approach to treating the psychobiological "causes" of mental disorders is the psychopharmacological approach. Essentially all psychotropic drugs affect neurotransmitter systems, however it is becoming clear that effects on receptors may be the most significant aspect of drug therapy. This article reviews receptor function and specific receptors known to be important in both the pathology and treatment of mental disorders. Copyright © 2000 Taylor & Francis.