This study attempts to determine whether selected personality and demographic information can be utilized to predict the length of stay of adolescents in an inpatient therapeutic program. Predictor variables included scores on the five Harris-Lingoes Psychopathic-Deviate subscales of the Minnesota Multiphasic Personality Inventory (MMPI), Wechsler Intelligence Scale for Children-Revised (WISC-R scores, and sex, age, parent, and sibling information. Data were collected from case files of 140 adolescents, ages 12 to 18 years, who had been admitted to a state hospital from 1979 to 1985. Each of these adolescents had obtained a score of 70 or above on the Psychopathic-Deviate (Pd) Scale of the MMPI. A preliminary correlational investigation of the data was conducted, followed by stepwise regression analysis. Regression analysis revealed that only sex and the presence of an older sister(s) were significant in prediction of length of stay of inpatient adolescents with elevated Pd scores.