Procedures for early identification of delinquency-prone youth in Eau Claire County, Wisconsin, are described in this report of a 1961-1972 study designed to delineate the problems of aggressive and disruptive classroom behavior as related to delinquency. Data collection began in 1961, when each 3rd-, 6th-, and 9th-grade teacher in Eau Claire County, Wisconsin, was asked to nominate 2 boys and 2 girls whose behavior was persistently aggressive and 2 boys and 2 girls whose behavior was persistently socially acceptable and productive (n=1550). This sample was then used for 3 previous phases of investigation (as reported in ED 014 335, ED 019 153, and ED 020 812) and for the present study, Phase IV. The method of investigation for Phase IV consisted of obtaining test scores and grades for the original 3rd and 6th graders; obtaining rank in graduating class for the original 6th and 9th graders; completion of The Behavior Problems Checklist for 12th graders; completion of social adjustment ratings by teachers on 8 aspects of behavior for 12th graders and the graduates; and collection of data from police and sheriff departments, welfare agencies, the juvenile court, a mental health agency, and the health department. From these data, variables were isolated for use in predicting academic achievement, social adjustment, health and welfare, and law contact. In the report, statistical analyses in terms of these variables are presented in tabular form, and manuals are provided for use in predicting behavior in terms of the variables that were isolated. (PS)