A new procedure is proposed for developing, evaluating, and implementing routing procedures for use with individualized instruction programs. An item response theory model for describing the relationship between performance on sequentially arranged units of instruction, and procedures for using the model to evaluate sequential relationships and for making routing decisions are discussed. A procedure for estimating the parameters of the model is described. Empirical data are presented to support the validity of the model. The model and procedures described appear to be useful and to merit continued research efforts directed toward their development. (DWH)