The early Yi Dynasty was the period in which the medical sciences and systems were most developed in the history of medical science in Korea. After King Yŏnsan, the development of the Korean medical science had been almost halted by the introduction of the medical science of the Ming Dynasty, which made the Korean traditional medicine gradually obsolete. To make it worse, Imchin waeran (the Japanese invasion of Korea in 1592) and Pyŏngchahoran (the Manchu invasion of korea in 1636) deprived Korea of the development of the medical science and technology. However, there had been some noticeable development in medical science. For example : 1. Tongŭi pogam was written by Hŏ Chun, and many able medical doctors were produced by the efforts of the King Chungchong and King Sŏncho who showed a great deal of interest in the development of medical science. 2. Imchin waeran gave a tremendous impact on the Japanese medical science and the introduction of the Ming medical science played a catalytic role in advancing the level of the Korean medical science. 3. The woman-doctor system was newly introduced to take care of women's disease exclusively. 4. The mid-Yi Dynasty exerted more efforts to advance the medical science based on the accumulation of the medical developments of the early Yi Dynasty.