Schizophrenia is a chronic and disabling disease that typically begins during adolescence or early adult life and severely impacts psychosocial functioning. There is no known single cause of schizophrenia. It is hypothesized that genetic factors and early neurodevelopmental abnormalities (including apoptosis, disruption of neuronal migration, or alteration of synaptogenesis) may confer a constitutional vulnerability to the disease. Subsequent environmental factors (including obstetric complications, exposure to viral infection in utero, or exposure to psychosocial stress during childhood) may then trigger the behavioral expression of this vulnerability, perhaps via subtle alterations of brain development. Within this framework, dysregulations of the dopamine (DA) and glutamate neurotransmitter systems have been most intimately associated with the physiopathology of schizophrenia. This chapter focuses on this aspect of the illness, with special attention given to the DA receptors.