The Emergency Medical Holographic Program (EMH) is a highly sophisticated hologram that has been present in the Star Trek universe ever since the Voyager series. By the 2370s, Starfleet had developed a fully functional holographic medical supplement, an artificial intelligence with a solid holographic body capable of assisting starship medical officers during emergencies, and even outright replacing them should the chief physician be incapacitated or killed. The EMH was originally developed by Dr. Lewis Zimmerman, regarded by Starfleet as the "father of modern holography".
- Intelligence - The EMH is capable of learning all manner of new skills and assets, normally by the simple introduction of a new subroutine into its holo-matrix. EMH's are also capable of learning on their own, as evidenced by The Doctor - the EMH aboard the USS Voyager - whose unique circumstances afforded him a great deal of freedom to expand his programming almost without limit. Even standard EMH programs possess the full knowledge of Starfleet's medicinal and physiological databases, allowing them to perform any and all medical procedures suited to the needs of all known alien species.
- Personality - Lewis Zimmerman based the personality of the EMH Mark One on his own personality. This turned out to be the program's undoing as Lewis himself was known to be arrogant, irritable and highly egotistical. Inheriting its creators flaws, the Mark One was poorly recieved by Starfleet and eventually bounced out of the medical corps. Future versions of the EMH would be programmed with more courteous and gentle personalities.
- Mark One - The EMH Mark One was modelled on Dr. Zimmerman's own physical likeness and personality. As a result, they were eventually bounced out of the Starfleet Medical Corps, much to Zimmerman's dismay. He tried to have the entire line decommissioned, but Starfleet had them all reassigned for menial labour in dilithium mines and waste transfer vessels. While in circulation, the Mark Ones were capable of performing over 5 million cross-species treatments and procedures from the collective knowledge of 2000 medical references and the experience of 47 Starfleet doctors. However, it possessed a poor bedside manner and often hesitated to perform certain tasks. The programs were also restricted to their sickbays, unable to travel beyond the range of their holo-emitters to provide assistance to injured crew members elsewhere on a ship or station.
- Mark Two - The Mark Two did not resemble Dr. Zimmerman but was modelled after a youthful human male with blonde hair. While its personality was regarded as a pleasant change to that of the Mark One, the original EMH-2 prototype aboard the USS Prometheus appeared to be anxious and somewhat scatterbrained.