This paper attempts to examine some ways medical knowledge was brought into practices, and also addresses its implications as a conclusion. Relying not merely on categorical medical texts in general but rather on medical case writings 醫案, I inquire into how doctors incorporated their practice-based knowledge with text-based theories -with what attitudes doctors mobilized their medical knowledge and in what ways they made diagnoses and composed prescriptions - in 18th and 19th century Joseon Korea. Exploration of the four medical case writings under our investigation leads to the following: in the 18th century, a doctor showed a process in which the then-received medical knowledge 古方 was deployed with conviction and put into use in the hands-on clinical practice, which arguably reflects his being connected to the metropolis-based bureaucratic experts network; in the 19th century, noticeably in the provincial regions away from the technical officials network, there emerged some doctors who kept themselves at a distance from predecessors’ knowledge and began to make their own ideas and experiences into a working knowledge, consequently speaking out for themselves.