This paper calls attention to the current need for systematic diagnostic assessment in the secondary schools. The social organizational pressures of the secondary schools and the limited professional preparation of school psychologists to work with adolescents are cited as the two principle reasons why school psychologists have not provided substantial amounts of service to the secondary schools. A data-based screening system is proposed to actively identify students with probable special education needs, as well as those who require specialized services within regular education. Individual diagnostic assessment of handicapped adolescents is discussed in relation to a total intervention plan which addresses four instructional areas--academic, vocational, social, and personal. The rationale for, and description of, specific assessment procedures are presented for each of the four areas. Implications for future directions in training and the practice of school psychology with adolescents in the secondary schools are discussed. A descriptive, objective referral form that assesses students in terms of academic task areas, academic subject performance, pre-vocational/vocational performance, speech and language, and auditory perception is also included. (Author/JAC)