Minimal brain dysfunction (MBD) has long been considered a disorder limited to childhood. A number of longitudinal and adoption studies suggest that MBD may persist into adult life where its existence is concealed by the application of a variety of diagnostic labels. In order to test the hypothesis that MBD does persist into adulthood, fifteen putative MBD adults were identified on the basis of current MBD-like complaints, self-description of MBD characteristics in childhood, and a parental rating (on a standardized form) of "hyperactivity" in childhood. Eleven of the fifteen subjects were given a double-blind trial of methylphenidate hydrochloride, or amitryptiline hydrochloride. Eight of the eleven showed a significant response to the double-blind trial of methylphenidate. Of the fifteen, eight showed a good response to stimulants or tricyclic antidepressants, two showed a moderately favorable response, and five were unresponsive to drug therapy.