Research has shown that truancy is one of the most reliable predictors of school dropout, which leads to a variety of deleterious outcomes for youth, including involvement in juvenile delinquency and later adult crime. Colorado officials have begun taking the problem of truancy more seriously by allowing schools to file a truancy petition with the juvenile court once a student has missed a specified number of school days due to unexcused absences. This study examined the effects and costs of sentencing youth to detention for truancy. Data under examination included interviews with juvenile magistrates from the 4 judicial districts in Colorado with the highest rates of detention for truancy; school records for 21 youth, both before and after their detention was served; 2 focus groups' data from 10 detained youth; and survey and school data collected from 30 detained youth. The findings indicate that most juvenile magistrates do not sentence truant youth to detention but rather view this option as a last resort. Four reasons were cited by the magistrates for sentencing truant youth to detention: to deal with defiance, to scare them straight, to keep them safe, and to access resources on the youth’s behalf. However, data from schools provided no evidence that detention improved either school attendance or achievement. Yet, according to self-reports, a minority of the detained youth believed detention had a positive effect on them. One of the most striking findings was the fact that many of the youth in this study remained in school despite being 16 years of age and legally able to dropout of school. Tables, footnotes, appendixes, bibliography