Compared changes in locus of control among 19 federal prison inmates who were graduates of a 9-mo residential cognitive substance abuse treatment program with 20 inmates selected from a waiting list. Both global locus of control, as measured by the Rotter's Internal-External Locus of Control Scale, and vocational locus of control, as measured by the Spector Work Locus of Control Scale, were examined. Treatment groups displayed significantly more internal loci or control across both dimensions. (PsycINFO Database Record (c) 2019 APA, all rights reserved)