A growing literature--most uncontrolled--suggests that lithium may be useful in the treatment of some non-manic-depressive personality disorders. The diabolical behavior, conversion symptoms, and diffuse violence and cruelty of a young woman responded remarkably to treatment with lithium. Blind substitution of a placebo confirmed a lithium effect. Patients with the DSM-II diagnosis of explosive, antisocial, and hysterical personalities would appear to be the best candidates for a trial of lithium.