First, several types of juvenile court records were analyzed to determine the kinds of information which most influence the delinquency sentencing decision. Both legal and social information were found to influence this decision. In particular, the harshest sentences were given to delinquents who were uncooperative, males, felons, and repeat offenders; they had broken homes, family instability, and emotional instability. Since adolescent crime tends to be committed by individuals of both sexes who come from all strata of society as well as family backgrounds, these data support the contention that juvenile court decisionmakers use implicit criteria to judge delinquents. The second study was designed to directly measure if juvenile court decisionmakers have theories about the information they use to sentence delinquents. Using a within subjects design, 20 probation officers and judges from 13 juvenile courts read 32 case histories of delinquents and rated 9 dependent measures. Analyses revealed that experts used the information to make inferences about delinquents in the areas of crime seriousness, need for counseling, need for court intervention, family influence, peer group influence, emotional instability, dangerousness, intentionality, and moral character. During the third part of the investigation, two experimental studies were conducted to explore the origins of experts' theories of delinquency by comparing them to those held by nonexperts. Community residents were given vignettes and questionnaires similar to those given to the experts. Overall, the results of these studies suggest that considerable agreement exists between juvenile court decisionmakers and community residents in their social judgments of delinquents. Study results suggest that methods and theory of social cognition may offer a promising new approach toward a better understanding of legal decisionmaking. Study data and over 200 references are provided.