Distributed Mission Training (DMT), the Air Force's concept of ground-based training using networks of real-time simulators and computer-generated forces, evolved from earlier programs including Distributed Interactive Simulation and Simulator Networking. In these programs, defined training objectives were often deliberately avoided and training benefits were presumed to result from the intrinsic feedback and lessons learned from battle engagements. Previous research has demonstrated that DMT can provide effective training tailored to meet defined learning objectives through careful development and delivery of scenarios that are presented in a building block format over several training sessions. Using this paradigm, however, assessment of trainee performance has been problematic since the scenarios contain many different elements and encompass a wide range of complexity. A process for developing an empirically based degree-of-complexity scale for scenarios is described. The resulting scale allows direct comparison of team performance over several days of training and will support improved linking of scenario content with training objectives.