Investigating programs and full-time personnel which provide special needs services at the postsecondary level in Minnesota Area Vocational-Technical Institutes (AVTIs), a study assessed variability in practitioner use of individual student diagnostic information and prescriptive services in individualized education program (IEP) development and variability in educator characteristics which influence their use of diagnostic-prescriptive processes. Research literature on diagnostic-prescriptive planning for handicapped students can be organized into three areas: the educational context leading towards IEPs, IEP content and concerns, and models and categories of diagnostic and prescriptive services. In a controlled case study approach, thirty-one individuals representing fifteen AVTIs completed questionnaires including two student case studies. Divided into four primary informational areas, the data collected show that (1) practitioners providing the same services differ in level of preparation, experience, assigned job duties, and perceived needs for additional training; (2) participant perceptions of their employing institutions indicated varying degrees of service availability; (3) no significant differences were found in the average amount of diagnostic information used, while particpants varied in IEP determination; and (4) standardized terminology and operational procedures impact on the development of appropriate IEPs. (The questionnaire and supplemental statistical analyses of data are appended.) (YLB)