Hospital psychiatry has evolved from long-term "treatment" programs that were primarily custodial to the successful pharmacological treatment of acute psychotic episodes. Unfortunately, many patients still return to the hospital with relapses. This so-called revolving door syndrome draws attention to the critical importance of preventing as well as treating acute episodes. In the first part of this overview, the author reviews the clinical literature on prophylactic treatment of schizophrenia with maintenance antipsychotic drugs. The second part will review the literature on prophylactic treatment of affective disorders with lithium and tricyclics. In the opinion of the author these drugs provide the potential for truly preventive psychiatry.