Questionnaires sent to jails, lockups, and juvenile detention centers in the Criminal Justice Agency List documented 383,328 children in secure detention facilities; 170,714 juveniles in adult jails; and 11,592 in adult lockups. Taking into account the response rate of 97.6 percent, the study estimated that 479,908 persons under age 18 were in all 3 types of facilities during 1978. The rate of suicide among juveniles in adult jails during this period was 12.3 per 100,000, which is 4.6 times larger than the suicide rate of 2.7 per 100,000 among youth in the general population during 1977. The rate of suicide of juveniles in adult lockups was 8.6 per 100,000. Unexpectedly, the suicide rate in juvenile detention facilities was only 1.6 per 100,000. It should be noted that this data probably underestimates the suicide rates in jails and lockups, since admitting that such events occur in an institutional setting is embarrassing. In addition, children stay in such settings for short periods and under supervision, so they have less time and more barriers to overcome to commit suicide than youth in the general population. The lower rate in detention centers may be attributed to their greater supervision and ongoing youth activities which counter the isolation often confronted in jails and lockups. Thus, the policy of incarcerating children in adult facilities may be contributing to a relatively high rate of suicide among those children. In this study, half of the 22 children who killed themselves while in jails and lockups had not committed a felony and presumably were not a danger to the community. Tables and approximately 50 references are supplied.