The example of schizophrenia is used to illustrate how sex hormones affect the presentation of illness and its treatment. Organization and activation effects of hormones are explained, and behavior is shown to result from a complex interplay of hormones, brain mechanisms, and social pressures. Sex differences in schizophrenia (in onset age, symptoms, antipsychotic, and other treatment) are consequences of this interplay and impact on the clinician's ability to diagnose, treat, prognosticate, and prevent the disability and distress of schizophrenia.