This report is an integral part of the publication series of the Youth in Transition study, a nationwide panel survey of adolescent boys, which attempts to discover and document how the contemporary social environments affect the development of young men during their high school years. Four waves of data were gathered from 2,213 boys comprising the sample, who were clustered into 87 different high schools throughout the country. Additionally, because of the special interest in the school environment, data were collected from the principals, counselors, and samples of teachers in the participating schools. The efforts reported in this study are based on the attempt to outline a practical procedure to be used in longitudinal analyses of Youth in Transition data, the major aim being to develop a strategy which can be applied to most, if not all, of the analyses to be performed. The report develops a "parallel prediction" model for longitudinal analysis, which makes separate use of each repetition of the criterion dimension; it is contended that the proposed strategy is widely applicable in studies employing panel designs. The proposed model was applied to a limited set of analyses of the Youth in Transition data. Early identification of subgroups was seen to have a facilitating effect in longitudinal analysis. (Author/RJ)