: Conventional antipsychotic drugs, although efficacious in the treatment of mania, have not demonstrated a significant usefulness in the maintenance treatment of bipolar disorder. This has primarily been due to a tendency to induce depressive symptoms and depressive recurrences in this group of patients in the course of long-term administration. However, the picture has changed following the introduction of second-generation antipsychotics. These drugs have pro-depressant properties (if any) that are much weaker than conventional antipsychotics. Furthermore, their tolerability, especially in long-term treatment, is more favorable compared to classical antipsychotics. Clinical observations of the action profile of second-generation antipsychotic drugs in the treatment of schizophrenia have pointed to a possibility of these agents possessing mood-stabilizing properties. The first such suggestion was made by Zarate (1995) in connection with clozapine. The prevention of manic and depressive recurrences in bipolar disorder is a hallmark of the definition of mood-stabilizers.