鈥� The use of pharmacologic agents in treating patients described as borderline generally has been accorded an insignificant, or at best, minor, role. We discuss this observation and review the literature that has dealt with this aspect of treatment. Diagnostic criteria are presented that appear to define a specific population of borderline patients who have been observed to be responsive to low doses of neuroleptic drugs. Five case histories of patients with conditions diagnosed and treated in this manner are presented, followed by a discussion of the implications of this approach in terms of clarifying the nosologic issues that have arisen around the "borderline" concept.