Advances in technology have led the U. S. Army to design the Classroom XXI Master Plan (U. S. Army Training and Doctrine Command, 1996). This plan includes the introduction of an in-class simulation, and student and instructor integrated computer workstations to support student-centered, experiential learning at higher levels such as officer advanced training. The plan also encourages the U.S. Army schools to experiment with the use of technology. We proposed that full exploitation of the advantages of new instructional technology could only be achieved through a review of the training requirements, the learning process, and their relationships to instructional media. To address this issue, a Concept Experimentation Program (CEP) effort was conducted by the U. S. Army Research Laboratory to support the U.S. Army Field Artillery School's (USAFAS) Classroom XXI development. Phase I of the CEP included 1) an analysis of the training tasks in the Field Artillery Officer Advanced Course (FAOAC), 2) a review of instructional literature, and 3) a review of current and potential instructional media. Based on our reviews, we concluded that a shift in the Army's current training paradigm to a process that is less linear is desired at the advanced level. Specifically, a constructivist approach informed by Cognitive Flexibility Theory would best support the Army's plan. The theoretical basis of the approach, our refinement of the student-centered learning process, the role of constructivist instruction as a precursor to simulation-based training, and resulting design principles are described. In Phase II of the CEP, we designed and developed proof-of-principle courseware to illustrate the concepts developed in Phase I. User input during Phase II is described regarding desired design features and factors of user acceptance. Requirements for more complete development include research to design instructional facilitation procedures, the need for cognitive authenticity in constructivist instruction, and integration of learner motivation factors in design and development.