Approved for public release, distribution is unlimited / Human Systems Integration Report / In the past few years, Massive Multiplayer Online Games (MMOG) have gained in popularity in the gaming industry, the public and the Department of Defense. Improvements to computer technology and the increased data transfer rate over networks have caused the potential applications for networked environments to blossom. MMOGs are a product of these improvements, as technological advancements have made it possible for the masses to gain access to virtual environments and participate. The ability to communicate and interact within the virtual environment has the potential to make MMOG technology an ideal tool for evaluating C4I systems. The design and evaluation of C4I systems with MMOGs has the potential to allow for exploration in the areas of warfighter effectiveness, emergent behavior, collective decision making, human systems integration and effective information flow. This thesis strives to illustrate how a C4I system modeled in an MMOG can aid designers in gathering insights on the effectiveness of the system in various combat situations. The insights will be gathered through the interactions of players with the modeled system in the virtual environment. The human interaction with the modeled C4I system provides the ability to capture the effects of the C4I system on the warfighter. The resultant effects of the C4I system on the warfighter directly contribute to the overall combat effectiveness of the deployed military forces. The background of MMOGs and C4I systems, and attributes of MMOGs that are desirable in evaluating C4I systems are introduced and discussed. FORCEnet, a global C4I architecture still in the conceptual phase is then used as an example to illustrate the potential rewards to using MMOGs to evaluate C4I systems. / Lieutenant, United States Navy