Instructional System Technology in recent years has been characterized by an increase in individualized instruction and the modularization of the curriculum. In traditional systems the learners are forced to take blocks of instruction the size of entire courses and these are much too large. The courses can now be broken down into conceptual subdivisions and these into series of modules. Each module has clearly stated behavioral objectives regardless of the nature of the intellectual performance prescribed in it. The test items of the module are derived from the objectives rather than from the instructional materials currently in use to attain them. The instructional materials for a module may be offered on different tracks which feature different levels of abstraction thus accommodating the different learning characteristics of individual learners. Most instructional system developers today are looking ahead to a time when good modules will be developed at many localities and circulated widely for use at various institutions. There is a growing need for a valid and widely applicable method of evaluating modules of instruction. Three basic criteria are relevant to the evaluation of a module of instruction: (1) the amount of learning that results, (2) the dollar equivalent cost to the instructional organization of providing the module, and (3) the amount of learner time consumed by interaction with the module. An example is given comparing three different versions of a module. (CK)