In this study of 649 delinquents, 109 persons were detained. 79 in preventive detention. A comparison of the personal characteristics, criminal behavior, and subsequent judicial processing of these juveniles with those other detainees and nondetainees suggested that youth detained to protect the community are more dangerous than other offenders and receive more restrictive dispositions than other detainees and nondetainees. A minority of youths in preventive detention are nonserious offenders who seem to pose little threat to the community. Juveniles detained for their own benefit include both serious and nonserious offenders, but few of this group of youths ultimately receive restrictive dispositions. The use of preventive detention seems to create a limited but self-fulfilling prophecy, for these youths are judged on their present conduct and predicted future behavior. Preventive detention appears to attach the stigma of guilt but not the stigma of future dangerousness. 5 tables, 3 notes, 1 case note, and 24 references. Detention criteria appended. (Author abstract modified)