Introduction: Recent evidence suggests that the prevalence of mental health disorders among youth entering juvenile pretrial detention centers is two to three times higher than youths in the general population (Teplin, Abram, McClelland, Dulcan & Mericle, 2002). Within the past five years, mental health screening upon entry to a juvenile justice facility has become standard practice across the nation. We know more about the validity and reliability of mental health screening tools used in this context than we do about the factors that facilitate their implementation. If tools are not implemented properly, their adequate validity is virtually lost. Effective screening procedures require attention to how screening instruments are put into place and how they actually function within juvenile justice facilities. Introduced in 2000, the Massachusetts Youth Screening Instrument—Second Version (MAYSI-2; Grisso & Barnum, 2006) is now the most widely used mental health screening tool in juvenile justice secure facilities in the United States.