Helmet mounted sights and displays are becoming basic requirements for new aircraft designs, upgrade programs, special mission applications and simulators. The common objective in all these efforts is to increase the mission effectiveness and survivability of the ground/air/space vehicle crew. This presentation will focus on the human integration of the helmet, display and sight subsystem functions to meet this goal. The specific intent of this information will be to impart a higher level of sensitivity to the importance of helmet subsystem functionality as it applies to the interrelated issues of protection, comfort, pilot interface, aircraft interface and supportability. Design and field experiences relative to current helmet mounted sight/display (HMS/D) production and development programs will be presented. Emphasis will be placed on the evolution of specific helmet subsystems based on performance specifications, mission requirements analysis, user evaluation and the subsequent but inevitable tradeoff analysis. The performance potential of any HMS/D will ultimately be judged by the physical interface to the user. When a piecemeal, one-display-fits-all approach is taken, the results can be both ineffective and hazardous. When a thorough, functionally integrated approach is applied to the physical interaction of an HMS/D application, the vehicle crew capability will improve dramatically. Many fixed and rotary wing programs as well as land vehicle demonstrations have conclusively demonstrated this over the past twenty years. This can be safely achieved without compromising the current base line crew comfort and crew-to-vehicle interface.