During the Ming dynasty, official institutions of medical learning were established throughout the country following the system used in the Yuan dynasty. Medical officers 醫官 for these institutions came mainly from medical households 醫戶 ─ a kind of professional household in which there was a long lineage of doctors. Itis interesting to note that the position of medical officer usually went to members of certain families. According to our research, this phenomenon occurred most frequently in Anhui and Jiansi, but there are also many cases seen in Zhili, Zhejiang, Huang, Fukien, Guangdong and Guizhow. Beginning in the middle of the 15th century, though, the position of medical officer could be obtained by making payments of grain or money to the government. As a result, the privileged position of certain families (especially minor families at the local level) was gradually lost and their development was arrested.