National estimates of juvenile court activity are based on an analysis of 560,400 automated case records from approximately 1,200 courts and on court-level summary statistics from more than 300 additional courts. Data indicate that U.S. juvenile courts handled an estimated 1,338,100 delinquency cases in 1991, a 5-percent increase over 1990 and a 16-percent increase over 1987. The most serious charge in 59 percent of all delinquency cases involved a property offense. In 1991, youths were detained at some point between referral and disposition in 20 percent of all delinquency cases. These 272,100 detentions represented a 19-percent increase over the number of cases detained in 1987. Drug law violation cases were the most likely to involve detention in 1991 (36 percent). Person offense cases showed the largest increase in the use of detention between 1987 and 1991 (52 percent). Half of all delinquency cases were handled informally by juvenile courts, and nearly half of informally processed cases were dismissed. In 1991, an estimated 9,700 delinquency cases were judicially transferred to criminal courts, a 39 percent increase over the 1987 level. Nearly half of all youths transferred to criminal courts were charged with property offenses. Youths were adjudicated delinquent in 59 percent of petitioned delinquency cases. Of cases in which youth were adjudicated delinquent, 29 percent resulted in out-of-home placement in a residential facility and 57 percent resulted in formal probation. In 1991, juvenile courts petitioned and formally handled an estimated 90,100 status offense cases, a 9- percent increase over the 1987 level. Status offenses involved liquor law violations (31 percent), truancy (29 percent), running away from home (17 percent), and ungovernability (12 percent). Runaway cases were more likely than other status offense cases to involve detention. Youth were adjudicated in 62 percent of petitioned status offense cases; 16 percent of these cases resulted in out-of-home placement in a residential facility and 63 percent resulted in formal probation. Appendixes contain a description of the survey methods, a glossary of terms, and a list of reported juvenile court cases disposed of in 1991 by U.S. county. 206 tables and 24 figures