About 500 juveniles were studied in this 3-year experiment. The facility had the capacity to hold 15 boys and 10 girls. The average length of stay was 15 days. Prior to the implementation of a time-out procedure, all staff (seven male and four female child care workers) were instructed in its use. Staff were required to record each occurrence of a time-out on a daily misbehavior sheet. The experiment used a one-group time-series design combined with elements of multiple baseline designs. The dependent variable was the frequency of antisocial behaviors measured by the frequency of time-outs. The independent variable (treatment variable) was the application of a short duration time-out. During almost three-fourths of the 36 months of the study, only 10 percent or less of the residents received a second time-out for the same behavior. The data indicate that the short duration time-out was effective in reducing the antisocial behaviors of 90 precent of the residents for most of the experiment. Figures and 10 notes are included.