DescriptionThis study examines the influence of moral development and course of antisocial behavior on mental disorder judgments of social work clinicians and social work students presented with clinically realistic vignettes meeting criteria for conduct disorder according to the fourth edition, text revision, of the Diagnostic and Statistical Manual of Mental Disorders (DSM–IV–TR; American Psychiatric Association, 2000). Clinical vignettes were designed to examine whether low moral development and life-course persistent antisocial behavior were interpreted as internal dysfunction, which is required by DSM–IV–TR to make a judgment of mental disorder. In a 3x3 design, vignettes were manipulated to include information about moral development and course of antisocial behavior as evidence of internal dysfunction, compared to a neutral condition. Vignette packets were mailed to experienced social workers and distributed to students in first-year MSW classes. Respondents (N= 241) answered the question “this youth has a mental disorder” for 3different vignettes. Vignettes were separated into three independent samples for logistic regression analyses, in which neutral vignettes were used as reference categories. Low moral development did not affect mental disorder judgments. The presence of life-course persistent antisocial behavior significantly increased the odds of a mental disorder judgment across three samples (OR=5.351, p<.001; OR=7.180, p<.001; OR=4.085, p<.001). The presence of adolescence-limited antisocial behavior significantly decreased the odds of a mental disorder judgment, (OR=.250, p= .006; OR=.345, p=.012; OR=.226, p=.001). Prior training in the use of DSM was significantly associated with disorder judgments (OR=3.145, p = .028). There were no interaction effects between level of moral development and the course of antisocial behavior. These findings indicate that social work clinicians and social work students may view life-course persistent antisocial behavior as evidence of internal dysfunction when making disorder judgments. Further, clinical disorder judgments may be influenced by training clinicians and students to use the DSM appropriately. Professional training in the identification of internal dysfunctions in making mental disorder judgments could improve diagnostic accuracy among social workers.