The Doctor of the USS Voyager, a noted EMH program

Subroutines composing an EMH holomatrix

For individual Emergency Medical Holograms, please see Emergency Medical Holographic programs.

The Emergency Medical Holographic program or Emergency Medical Holographic system, also known as the Emergency Medical Hologram (EMH) or Emergency Holographic Doctor, was an adaptive holoprogram developed during the 2360s by Starfleet and used on a number of Federation starships during the late 24th century.

It was designed to provide short-term advanced assistance during emergencies in sickbay to the extent of literally replacing a starship's medical officer. (DS9: "Doctor Bashir, I Presume") By 2377, there had been four versions of the EMH, designated Mark I thru IV. (VOY: "Life Line")



One of the earliest known concepts for a "holographic doctor" was first considered, if not rhetorically, by Enterprise NX-01 Commander Trip Tucker. In 2151, Tucker argued to Ezral – a Kantare engineer who had programmed several holograms of his former crew on behalf of keeping his daughter, Liana, company – that, with regards of her welfare, "What if she gets hurt? What do you do then? Program a holographic doctor?" Ezral, nevertheless, responded simply that "we've survived here successfully" without one. (ENT: "Oasis")

Over a century later, while testing the ill-fated M-5 multitronic unit aboard the USS Enterprise, Spock lamented to Dr. Leonard McCoy on the misfortune that computer programming had not yet advanced far enough to immediately replace starship surgeon. McCoy retorted that he'd rather resign than be replaced.

Later, following the demise of the M-5, McCoy observed that "compassion [was] the one thing no machine ever had. Maybe it's the one thing that keeps men ahead of them." Nevertheless, Spock still commented on the idea that, if using McCoy's memory engrams as a template for the technology used in creating the M-5, "the resulting torrential flood of illogic would be most entertaining." (TOS: "The Ultimate Computer")

By the mid-24th century, however, sufficient advancements in the field led Starfleet to commission the holo-engineer, Dr. Lewis Zimmerman, to begin work at the Jupiter Station Holoprogramming Center on the new EMH program. One of the EMH's predecessors was the hologram Haley, first activated in 2368. (VOY: "Projections", "Lifesigns")

EMH Mark I



The Emergency Medical Holographic program (EMH) was formally known as an "EMH Program AK-1 Diagnostic and Surgical Subroutine Omega-323", though Zimmerman wanted to call his creation the "Holo-Doc", but Starfleet Command made the request to name the hologram "Emergency Medical Hologram" instead. (VOY: "Projections" ) The persona was not, however, given a formal name. (VOY: "Lifesigns")

The bit of information from "Projections" was seen on a small viewscreen okudagram detailing Zimmerman's life and work history.

The design work began around the 2360s, where it took the greatest holo-engineers in Starfleet years to develop the EMH. Among those eventually involved included Reginald Barclay. (VOY: "Message in a Bottle", "Projections", "Life Line") Following its creation, thousands of holograms based on that technology were created for various functions. (VOY: "Life Line")

The EMH was designed as "an incredibly sophisticated computer simulation," and "the embodiment of modern medicine." (VOY: "Lifesigns", "Parallax") The EMH program specifications, which were at the time considered quite "impressive", included the entire Starfleet Medical Database. In all, it contained over five million medical protocols – ranging from possible treatments to surgical procedures (including one developed by Dr. Leonard McCoy), the collective medical knowledge of over three thousand cultures (including every Federation world), it further possessed information from two thousand medical reference sources (including Gray's Anatomy and Comparative Alien Physiology), and the experience of 47 individual medical officers. (VOY: "Parallax", "Ex Post Facto", "Lifesigns", "Meld", "Message in a Bottle", "Relativity", "Virtuoso", "Critical Care") Above all, the EMH was programmed with the Hippocratic Oath. (VOY: "Darkling", "Critical Care"; PIC: "Broken Pieces")


It was designed and programmed solely as a short-term emergency supplement to the medical team otherwise found aboard a starship, until a permanent replacement could be found, and therefore, was only meant to function for a maximum of 1,500 hours (62.5 days); after this time, memory degradation would occur. (VOY: "Caretaker", "The Swarm")

A diagram of The Doctor's memory files

The EMH was also supplemented with contingency programs and adaptive programs to learn while serving as a supplement of a normal medical staff in cases of emergency. (VOY: "Ex Post Facto") It contained fifty million gigaquads of computer memory, which was "considerably more than most highly developed humanoid brains." (VOY: "Life Line") Memory files were stored in the EMH memory core, where memories concerning a specific subject or period of time could be deleted. (VOY: "Latent Image") Additionally, while not designed to act as ship's counselor, the EMH had been programmed with sufficient psychological knowledge to note observational concerns. (VOY: "Darkling")

Beginning around 2370, the entirely new EMH system began to see installation aboard newly launched Intrepid-class and Nova-class starships. (VOY: "Equinox", "Relativity") By 2371, Starfleet was still being considered for installation throughout the rest of the fleet. (VOY: "Relativity") In all, 678 Mark Is were eventually created. (VOY: "Life Line")

Starfleet later requested that Dr. Zimmerman design an EMH supplement, designed to operate as a full-time doctor in any posting where life support or living space was at a premium and the primary mission did not require the doctor to leave sickbay. As a result, the research and design for the Long-term Medical Holographic program (LMH) was begun in mid-2373. While Deep Space 9 did not have an EMH installed initially, as it was incompatible with the station's Cardassian technology, one was later installed that year as a way to transfer its data into the LMH. (DS9: "Doctor Bashir, I Presume")

Design flaws

"Oh, yes, yes, yes, yes. You're the Mark I EMH. The inferior program."
"Beady eyes, terrible bedside manner. I recognize you."

Dr. Zimmerman, proud of his achievement, decided to program the EMH with both his physical, and most notably, psychological characteristics. (VOY: "Life Line")

Although later deemed to be a design flaw, the EMH had a rather acerbic personality, due primarily to the fact that it was "designed to practice medicine as efficiently as possible," enhancements, such as carrying on small talk or knowledge of "pithy Earth trivia" was viewed by its programmers as means of cluttering up its memory and compromising its performance. (VOY: "Persistence of Vision", "The Swarm", "Future's End, Part II", "Relativity") Some biological Starfleet doctors even went so far as to object to the use of the EMH. Doctor Beverly Crusher swore that she would never use one, although she was forced to do so in order to create a distraction while the Borg tried to assimilate the USS Enterprise-E, allowing her, her medical staff, and her patients, notably Lily Sloane, to escape from sickbay. (Star Trek: First Contact)

Eventually, it was concluded that the EMH Mark I was defective and they were retired from the Medical Corps. One key factor being that Dr. Zimmerman did not take into account that his own personality, given as that of the EMH, resulted in a poor bedside manner for a medical doctor. The resulting hologram was arrogant and irritable, and as a result was poorly received by many Starfleet doctors. This, in turn, spawned nicknames like "Emergency Medical Hotheads" and "Extremely Marginal Housecalls." According to Zimmerman he tried to save face and have them decommissioned, but "Starfleet, in its infinite wisdom, overruled me and reassigned them all to work waste transfer barges." (VOY: "Life Line") Later, the Mark Is were also deployed in other menial tasks, like dilithium mining. (VOY: "Author, Author")

Several EMH Mark Is mining dilithium


The fact that the reconfigured Mark Is could view holonovels suggests that they retained at least some level of sentience left over from their original medical programming.

Notable extended service

The most notable EMH in Zimmerman's series was the Mark I installed aboard the USS Voyager, known simply as The Doctor. The Doctor, who ran almost continuously for eight years, far exceeded the abilities of his original programming, and was forced to expand his programming extensively to keep up. This EMH originally objected to being the replacement for the entire medical staff, and after having had surpassed its expiration date, its life was fortunately extended with the help of his colleagues, and his program was altered to overcome this shortcoming. (VOY: "The Swarm")





A second generation EMH





Neither the Mark III nor Mark IV programs were shown on-screen, nor was it revealed what happened to the Mark II.

Late century design

By late century, EMH programs, as well as variations on the "emergency" theme, were all incorporated into the customizable Emergency Hologram basic installation, which was available for civilian use. Such packages were available onboard Kaplan F17 Speed Freighters. (PIC: "Absolute Candor", "The Impossible Box")

32nd century design

Eli, a EMH

EMH programs continued to be used by the Federation and Starfleet. One, known as Eli, served as medical officer under Admiral Charles Vance at Federation Headquarters in 3189.(DIS: "Die Trying", "There Is A Tide...")




The EMH's imaging system and tactile acuity subroutines allowed him to perform, "and in many cases improve upon, the most delicate tactile maneuvers required by a dizzying array of surgical procedures." (VOY: "Lifesigns")

When he was first activated, the Mark I EMH did not have the ability to deactivate himself after he finished his duties. (VOY: "Eye of the Needle") Auto-initiation of the EMH program could be achieved when a ship-wide red alert was initiated. (VOY: "Projections")

Written as a supplement to USS Voyager's EMH, The Doctor was given the ability to self deactivate by issuing computer command "Override Command 1-EMH-Alpha; End Program". (VOY: "Jetrel") Though seemingly unrelated, this was a standard feature for the EMH Mark II. (VOY: "Message in a Bottle")


See also



Despite Doctor Crusher's distaste for the EMH, she was forced to activate the EMH of the Enterprise-E during the events of The Q Continuum trilogy, when the Enterprise was attacked by the Calamarain during a mission to the Galactic barrier.

In the Star Trek: Prometheus trilogy, it is revealed that, even after the upgrade to the Mark III and Mark IV EMH, the Prometheus has retained the Mark II, even giving him the nickname 'Tre' for his habit of carrying around a tricorder when he can make such diagnostics on his own.

In Star Trek Online's Federation tutorial, players encounter a new version of the Emergency Medical Hologram (EMH Mark VI) serving aboard the USS Khitomer. Resembling a Vulcan with silver hair, this EMH, in dialogue released on YouTube but not included in game, claims to have a "personality matrix [that] combines qualities of more than twenty physicians, scientists, and counselors – including Admiral Beverly Crusher of Starfleet Medical, Ambassador Spock, and Ghee P'Trell of Andoria." He is voiced by Zachary Quinto. [1] Also in Star Trek Online, Emergency Medical Holograms, alongside the new Emergency Engineering Holograms and Emergency Security Holograms, can be acquired as Duty Officers. [2]

External link

Emergency Medical Hologram at Memory Beta, the wiki for licensed Star Trek works
