Over 200 professionals from schools in Minnesota participated in a computer simulated investigation of psychoeducational assessment and decision making for handicapped children. Demographic data were collected from each subject; estimates of the incidence of various handicapping conditions and knowledge of assessment was evaluated by a pretest. Each S read referral information about a child (one of 16 cases varying in terms of sex, socioeconomic status, physical attractiveness, and problem), and then accessed assessment information from seven domains (scores, qualitative information about performance, and/or technical information about the device). Eligibility, classification, prognostic, and placement decisions then were made for the child. Each S also indicated the extent to which various factors influenced decisions made, and answered questions about the efficacy of the computer simulation approach to the study for each research question; analyses of the findings as a function of referral information, professional role, and assessment knowledge are presented. Appended is the technical supplement which includes information on the diagnostic simulation program, examples of the student's scores on assessment devices, figures and tables presenting representative data of the school psychologists, and the actual case folder information presented to Ss. (Author/DB)