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Key Points

  • MYCIN was advanced for its time and had a competence level comparable to blood infection specialists and greater accuracy than general practitioners. The thought processes that it used were similar to human thought.
  • Researchers wrote this system in Lisp, a set of multiple programming languages designed to work with artificial intelligence. This system was the first system of its kind invented for medical usage.
  • MYCIN’s foundations came from another framework developed at Stanford called DENDRAL. This system helped find new chemical compounds in the organic chemistry field.

MYCIN was a backward chaining expert system which used artificial intelligence. It used this to identify the cause of serious infections and to recommend which antibiotics should be used to treat it. It could also recommend the correct dosage based on the weight of the patient. It could also be used to identify and diagnose several blood clotting diseases. MYCIN operated using a base of approximately 600 rules and various yes/no questions. It was then able to identify the bacteria based on the high or low probability of each type being responsible.

MYCIN Expert System: History

MYCIN Expert System
MYCIN was an expert system using backward chaining, a form of artificial intelligence.

MYCIN was developed by Edward Shortcliffe over a period of five or six years. At the time, he was with the Department of Medicine and Computer Science at Stanford University School of Medicine. During its usage, this expert system provided recommendations about antibiotics to use for patients with meningitis. Advantages of this system included a high degree of accuracy; however, disadvantages included not exceeding human competency levels to that high a degree.

Quick Facts

Edward Shortliffe
Original Use
MYCIN Expert System was a backward chaining expert system that was one of the earliest uses of artificial intelligence. Uses involved identifying bacteria occurring in blood infections and meningitis, among other bacterial infections. Another benefit was to find the right antibiotics for the type of infection and the proper dosage.

MYCIN Expert System: How It Worked

MYCIN used a form of artificial intelligence to determine if a patient had an infection and which antibiotics should be used to treat it.


MYCIN was an expert system using backward chaining, a form of artificial intelligence. In this context, backward chaining helped determine that the patient had an infection and worked back through several steps to determine the type of bacteria and which antibiotics to use. Advantages included making it easier to find out the causes because of the known endpoint.

MYCIN used a system of approximately 600 rules and a number of yes/no questions to identify the probability of each different type of bacteria being the one causing the infection. It could then rank these as high and low probabilities and then determine the best type of antibiotics to be used to treat it. It could also identify the correct dosage of antibiotics based on the patient’s weight.

MYCIN Expert System: Historical Significance

Experts describe MYCIN Expert System as having laid the foundations for all similar systems, making the design stand out in computer history. Although disadvantages included having an acceptable, rather than a high level of accuracy, this tool helped pave the way for further advancement in artificial intelligence. The system saw a lot of testing but never saw use in a clinical setting.

Researchers have learned from the advantages and disadvantages of this system to use its foundation ns in other applications. Examples of expert systems that have used similar technology include PXDES and CaDet, which medical professionals use to predict and identify cancer.

MYCIN Expert System: The First AI Medical Diagnosis FAQs (Frequently Asked Questions) 

When was MYCIN Expert System invented?

MYCIN was invented in 1972 when Edward Shortliffe developed the system with a team from Stanford University.

What is MYCIN Expert System?

MYCIN was designed to help identify bacteria that cause blood infections and other severe infections like meningitis.

What is the MYCIN system?

The MYCIN System was a computer-based system physicians used to identify blood infections and the most appropriate treatments.

How does the MYCIN expert system work?

The MYCIN Expert System used backward chaining technology to diagnose infections based on symptoms and medical history and recommend treatment based on the data received.

What does MYCIN mean?

MYCIN refers to a backward chaining expert system that helped diagnose and suggest infections, named after a typical class of antibiotics in use.

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More from History-Computer

  • Britannica Available here: https://www.britannica.com/technology/MYCIN
  • Expert System Available here: https://expertsystem101.weebly.com/mycin.html
  • Section Available here: https://www.section.io/engineering-education/forward-and-backward-chaining-in-ai/
  • Guru99 Available here: https://www.guru99.com/expert-systems-with-applications.html
  • Science Direct Available here: https://www.sciencedirect.com/science/article/abs/pii/S0020737378800492