• A review of all properly controlled studies clearly indicates that lithium carbonate is prophylactic for mania in bipolar patients; it is suggestive of prophylaxis for depression in both bipolar and unipolar patients. Studies are outlined that would clarify lithium carbonate's prophylactic effect for depression in these two patient groups. Continuation therapy with antidepressants reduces incidences of recurrence in unipolar depressives. The only controlled study indicates that tricyclic antidepressants may have prophylactic effect in unipolar patients. This finding needs confirmation. Data are insufficient for conclusions on prophylactic treatment for schizoaffective disorders.