The improvement in the clinical methods of identifying borderline subjects makes it necessary to reevaluate the efficacy of the treatment offered them. A random sample of 52 borderline and schizotypal patients was treated with two major neuroleptics, thiothixene and haloperidol, in a double-blind study. Eighty-four percent were markedly to moderately improved at 3-month follow-up; the patients responded better to thiothixene than to haloperidol. The main areas of positive response were those of cognitive disturbance, derealization, ideas of reference, anxiety, and depression. The patients also showed improvement in self-image and social functioning. There was no significant relationship between diagnosis and outcome of treatment.