As we enter the 21st century, military medicine struggles with critical issues. One of the most important issues is how to train medical personnel in peace for the realities of war. In April, 1998, The General Accounting Office (GAO) reported, "Military medical personnel have almost no chance during peacetime to practice battlefield trauma care skills. As a result, physicians both within and outside the Department of Defense (DOD) believe that military medical personnel are not prepared to provide trauma care to the severely injured soldiers in wartime. With some of today's training methods disappearing, the challenge of providing both initial; and sustainment training for almost 100,000 military medical personnel is becoming insurmountable. The "training gap" is huge and impediments to training are mounting. For example, restrictions on animal use are increasing and the cost of conducting live mass casualty exercises is prohibitive. Many medical simulation visionaries believe that four categories of medical simulation are emerging to address these challenges. These categories include PC-based multimedia, digital mannequins, virtual workbenches, and total immersion virtual reality (TIVR). The use of simulation training can provide a risk = free realistic learning environment for the spectrum of medical skills training, from buddy-aid to trauma surgery procedures. This will, in turn, enhance limited hands on training opportunities and revolutionize the way we train in peace to deliver medicine in war. High-fidelity modeling will permit manufacturers to prototype new devices before manufacture. Also, engineers will be able to test a device for themselves in a variety of simulated anatomical representations, permitting them to "practice medicine".