This research project evaluated seven competing hypotheses concerning the effects of LD on self-reported delinquency, the probability of being taken into custody by police, of being adjudicated delinquent, and committed to a juvenile corrections facility. The sample was selected from Baltimore, Indianapolis, and Phoenix during 1977 and 1978 and consisted of 972 teenagers from public schools not previously adjudicated and 970 youths officially adjudicated delinquent by the courts. The boy's average age was 15, and they came from varied ethnic backgrounds. Schools records, standardized test schools, and behavior observations were used to assess LD's, and all boys were interviewed. Boys with LD had significantly overall higher rates of delinquent behavior. LD youths were especially more likely than non-LD peers to have committed violent offenses, used alcohol and marijuana, and been more disruptive in school. The likelihood of having been arrested and adjudicated was substantially higher for LD youths. The greater delinquency in LD teenagers could not be explained by sociodemographic characteristics or a greater tendency to disclose socially disapproved behaviors. LD boys had experienced greater school failure and this contributed to increased delinquency. The data supported the susceptibility hypothesis which holds that among boys who had equally poor school attitudes, those with LD would engage more frequently in criminal activities. LD teenagers had higher probabilities of arrest and adjudication than non-LD teenagers, suggesting that their cognitive and social deficiences prevented them from contributing effectively to their defense in court. Among adjudicated delinquents, those with LD were not more likely to receive a more severe disposition from the court. Implications of these findings for research and public policy are discussed. Tables, over 130 references, footnotes, and supplemental materials from the analysis are supplied.