Abstract
Currently, educators lack longitudinal data measuring both the qualitative and quantitative outcomes of various educational interventions used with handicapped students. As a result, there is no reliable standard to use when designing instructional programs which meet the “criterion of ultimate functioning ” (Brown, Nietupski, & Hamre-Nietupski, 1976). The criterion of the least dangerous assumption is presented as an interim standard to use until such data are available. The criterion of the least dangerous assumption holds that in the absence of conclusive data educational decisions ought to be based on assumptions which, if incorrect, will have the least dangerous effect on the likelihood that students will be able to function independently as adults. The use of the criterion of the least dangerous assumption in instructional program design, parent involvement, and student evaluation of students with autism is illustrated.