The Department of Defense weapon system development and acquisition process requires that an operational effectiveness analysis be provided at every major decision point. The authors propose that these operational effectiveness analyses would be significantly enhanced by integrating the weapons system's manned research and development simulators with distributed interactive simulation (DIS) networks that provide large-scale, human-in-the-loop battlefield environments. Initial integrations should be designed to provide intellectual, hardware, and software "tool kits" for future integrations. The report outlines, and recommends as a proof of principle, the integration of the Crew Station Research and Development Facility (CSRDF) rotorcraft simulator operated by the Army and NASA with a fidelity-enhanced version of the Army Aviation Test Bed (AVTB) that incorporates the SIMNET-based simulator networking technology developed by ARPA. The integration emphasizes fidelity, validation, correlation, and calibration, which are the critical aspects of weapon systems analyses, and goes well beyond simply establishing communication interfaces to create a DIS environment.