En-route Criterion Levels (ECLs) are defined as decision rules for predicting pupil readiness to advance through an instructional sequence. This study investigated the validity of present ELCs in an individualized mathematics program and tested procedures for empirically determining optimal ECLs. Retest scores and subsequent progress were validating criteria. Results indicated empirical data can identify more efficient ECLs than those established a priori. To justify the cost involved, however, such data should be collected by the instructional designers during the formative evaluation field test of a program, using automated data processing and multiple-matrix sampling techniques. (Author)