Objectives : Our study aims to help users take the medicinal materials in a desirable manner by providing toxic and contraindicating information, based on the ontology of medicinal materials in traditional Korean medicine (TKM). Methods : The toxic and contraindicating data are extracted for 160 medicinal materials from 67 books published in Korea and China. The extracted data are linked to the medicinal material in the ontology, respectively. Results : We in this paper construct an ontology for toxic and contraindicating data of medicinal materials in traditional Korean medicine (TKM), extending our conventional ontology. Based on the ontology, we devised a web-based searching tool that enables users to share the toxic and contraindicating information of medicinal materials. Conclusions : The contents in our ontology are facts based on the books, while the addition of clinical knowledge may elaborate the ontology. Moreover, the addition of easy explanations for terminologies in our ontology is required to help users which are not familiar to TKM.