The juvenile justice system needs a tool that can identify and assess mental health problems among youths quickly with validity and reliability. The goal of this article is to evaluate the racial/ethnic and gender differential item functioning (DIF) of the Massachusetts Youth Screening Instrument-Second Version (MAYSI-2) using the Rasch Model. Data are presented from 3,906 assessments of male and female juvenile offenders between 13 and 17 years of age who are incarcerated in the California Youth Authority. DIF is identified in some items, raising concerns about the Suicide Ideation subscale as well as the Traumatic Experiences subscale that may require some further examination and revision. (Contains 5 tables.)