Assessed the efficacy of Gestalt therapy for a group of 9 hard-core criminals as compared with 9 hard-core criminals who met together but were not given Gestalt therapy. Ss were tested in prison before and after intervention using an instrument to measure internal locus of control and the degree of assumption of personal responsibility. Findings in these areas, in addition to the observations of the prison's social worker, confirm the effectiveness of the Gestalt therapy. The Gestalt methods seemed to be especially suited to Ss in a prison population because of their reluctance to identify with the normative social value system and because of their limited verbal skills. (PsycINFO Database Record (c) 2016 APA, all rights reserved)