This volume describes a test of a theoretical explanation of delinquency and dropout in terms of four variables: (1) aspiration-opportunity disjunction, (2) internal-external attribution of blame, (3) alienation or normlessness, and (4) access and exposure to delinquent groups. In this research a type of cluster sample was used in which the basic sampling unit was a school, rather than a person. All of the eight schools in the sample were located in metropolitan areas; seven in southern California, the other in the northern part of the State. All students who entered these schools as ninth graders in September 1963 comprised the target population; the study population consisted of 2,617 students. A longitudinal design was employed. Data were gathered in the period from September 1963 to September 1967. Initial observations were obtained when the study population entered the ninth grade, and additional data were collected annually until the usual date of graduation from high school for the cohort. The first observations were calculated to precede dropout and extensive involvement in delinquent behavior in order to permit assessment of postulated cause-effect relationships. Five hundred and fifty-eight persons were classified as dropouts during the course of the study; they left school 674 times. (Author/JM)