Nineteen Medicaments of Mutual Antagonism currently belong to pharmaceutical incompatibility and some of them cannot be used in a same prescription: if they are used in a prescription, the treatment effect is rather reduced or toxic response may be produced. Therefore. inthisstudy, it was intended to look about how Nineteen Medicaments of Mutual Antagonism were defined through survey of literatures and to review the meaning and clinical potential. According to "Sinnongbonchogyeong," "Medicaments contain the substance that suppress toxins and the toxins may be removed with use of mutual restraint or mutual detoxication substances" and they have been used in terms of this concept. Since Tang and Song era, mutual restraint and mutual inhibition were confused and were difficult to be distinguished. In terms of pharmaceutical incompatibility, the original meaning of mutual restraint was deteriorated in "Sinnongbonchogyeong". That is. mutual restraint has been used as the concept of mutual inhibition or incompatibility. When various literatures were reviewed. it could be found that Nineteen Medicaments of Mutual Antagonism were firstly included in the phrases of songs and then in "seven emotion." It could be supposed that Nineteen Medicaments of Mutual Antagonism was created based on the clinical experiences of the author and the influence of doctors. Such supposition means indicates that the interactions among medicaments could effectively be applied and mutual restraint did not belong to pharmaceutical incompatibility. However. many doctors used mutual restraint and mutual inhibition in clinical practice with no distinguishment since Song era and. especially, it is supposed that. when medicaments were used with mixing. the pharmaceutical incompatibility of "Nineteen Medicaments of Mutual Antagonism" or "Eighteen Incompatible Medicaments" were emphasized and influenced on the efficacy of pharmaceutical preparations or acted as an obstacle in treating diseases. That is. an error was transferred: mutual restraint and mutual inhibition were not distinguished and were discretionally added or deleted through common people or professionals with no specific verification. The pharmaceutical preparations that belong to Nineteen Medicaments of Mutual Antagonism belong to pharmaceutical incompatibility but. when reviewed various literatures and clinical reports. they are not thought to be the ones that can never be used. Therefore. systematic literature review and experimental research should be performed.