Although the Instructional Systems Development (ISD) model, based on behavioral theory, has been in use for several years, especially in military training, applying the systems approach to the curriculum development of on-the-job training material is a new use for it. The ISD model consists of five steps: (1) analyze system requirements; (2) define education/training requirements; (3) develop objectives and tests; (4) plan, develop, and validate training; and (5) conduct and evaluate training. ISD allows for continuing changes in the instructional system to match changes in the operational system shown in the model as a two-way feedback loop which runs between all steps. Changes identified in any step of the model can be compensated for by changing the system where needed. This flexibility, afforded by ISD, coupled with the "front end loading" of basing the whole instructional system on operational requirements, makes on-the-job training programs uniquely practical and economic. (The author illustrates the use of the ISD model for curriculum development of on-the-job training materials through the development of the Qualification Training Package.) (KC)