In East Asia during the second half of the 19th century, overseas mission work by Protestant churches thrived. Missionaries built schools and hospitals and effectively used them for evangelism. In the 20th century when Social Gospel Movement was expanding, medical work has been recognized as a significant mission service in and by itself. This article reviewed the construction and characteristics of missions work conducted by Canadian Presbytery; missionary doctors and Korean doctors who worked at the mission hospitals; why the missionary medical work had to stop; and career paths taken by Korean doctors upon liberation from Japanese occupation. The Canadian Presbytery missionaries, unlike other denomination missionaries, were rather critical of Imperial Japan, but supportive towards Koreans. This could have stemmed from the reflection of their own experience of once a colony of British Empire and also their value system that promotes egalitarian, democratic and progressive theology. The Sung-jin and Ham-heung Mission Bases were a community, interacting organically as a 'Triangle of Church, School and Hospital.' The missionaries mobilized the graduates from Christian schools and organized a Young Men's Christian Association (YMCA). Some of the graduates were trained to become medical doctors or assistants and worked at mission hospitals. Missionary doctors' approaches to balancing evangelism and medical practice varied. For example, Robert Grieson went through confusion and struggled to balance conflicting roles as a pastor for evangelism and also as a physician. Kate McMillan, on the other hand, had less burden for evangelism than Grieson, and focused on medical work by taking advantage of the opportunity that, as a woman, she can easily approach Korean women. Still another case was Florence Murray who practised evangelism within the hospital setting, and successfully carried out the role as a hospital administrator, going beyond 'women's work' as McMillan did. Korean doctors and assistants who worked at the mission hospitals had seen the spread of Protestantism in their youth; had received modern education; had experienced the fall of own country in 1910 and nationwide protest against Japan in 1919. The majority of them were graduates of Severance Medical College, the hub of missionary medicine at the time. After the resignation from the mission hospitals, 80 percent of them became self-employed general practitioners. The operations of the mission hospitals began to contract in 1930 due to tightened control by Imperial Japan. Shrine worship imposed on Christians caused internal conflict and division among missionaries and brought about changes in the form and contents of the mission organization. The incidence of the assault of Dr. Grieson brought about the dissolution of Sung-jin mission base and the interruption of the operation of Je-dong Hospital. As the Pacific War expanded, missionaries were driven out of Korea and returned home. In conclusion, the missions work by Canadian Presbytery missionaries had greatly impacted Protestantism in Korea. The characteristics of Canadian Presbytery were manifested in their support of Korean nationalism movement, openness for Social Gospel, and maintaining equal footing with Korean Christians. Specifically we note the influence of these characteristics in Chosun doctors who had worked in the mission hospitals. They operated their own hospitals or clinics in a manner similar to the mission hospitals by providing treatment for poor patients free of charge or for a nominal fee and treating the patients in a kind and humanistic way. After the 1945 Liberation, Korean doctors'career paths split into two directions. most of them defected to South Korea and chose the path to work as general practitioners. A few of them remained in North Korea and became educator of new doctors. It is meaningful that former doctors of Canadian missionary hosptal became dean of 2 medical colleges among 3 of all in early North Korea. This article does not cover the comparative analysis of the medical work by the missionaries of Canadian Presbytery and other denominations. It is desirable to include this analysis of the contents and the comparison in a future study of Korean doctors who participated in the mission hospitals, by denomination and by geographical region.