Research on criminal court sentencing patterns has suggested that young adults are treated more leniently than older adults, largely because of restrictions on juvenile record information. This study collected data on offense characteristics, juvenile and adult criminal records, and dispositions for 1,314 cases in Los Angeles, 963 cases in Las Vegas, and 273 cases in Seattle. These samples were stratified to ensure equal distribution among the age groups of 16-17 (juveniles), 18-20 (young adults), and 21-25 (older adults). Controlling for offense and prior record severity, the study found that in most instances young adult defendants were more likely to be convicted and incarcerated than defendants in any other age range. In all three sites, juveniles and young adults with extensive juvenile records generally were sentenced more severely than those with lighter records. The severity of the defendant's prior record did not affect case disposition for young adult burglars in Los Angeles, possibly because of the common practice of settling many burglary cases as misdemeanors. King County, Wash., has the best access to juvenile records, but it generally sentenced young adults the most leniently. The majority of juvenile arrests do not result in a finding of delinquency, but these charges currently are used to represent the defendant's history of delinquency. Thus, an unexplored issue is whether this use of unsubstantiated arrest information may contribute to incorrect prediction of subsequent criminality. Tables, graphs, and 32 references are supplied.