MYCIN — ранняя expert system, разработанная для помощи в диагностике и рекомендациях по лечению бактериальных инфекций. Она исторически важна для artificial intelligence, поскольку продемонстрировала rule-based reasoning в специализированной medical domain.
An early backward chaining expert system that used artificial intelligence to identify bacteria causing severe infections, such as bacteremia and meningitis, and to recommend antibiotics, with the dosage adjusted for patient's body weight – the name derived from the antibiotics themselves, as many antibiotics have the suffix "-mycin". The MYCIN system was also used for the diagnosis of blood clotting diseases.