Abstract: The cantharidin of Meloidae has long been used medicinally forits irritant properities, both in China and in western countries. In China its mediccinal usage may trace far back as 1-2 B. C. in "Shen Nong Materia Medica". In a book on Chinese herbal medicine, "Compendium of Materia Medica" (1596), written by the famous pharmaceutist, Li Shi-zhen of Ming Dynasty, about four hundred years ago, the author described four different kinds of meloid-beetles; by textual research we regard that they are referred to four different genera, namely:Epicaura Redt. (葛上亭长), Lytta Fabr. (芜菁), Mylabris Fabr. (斑蟊) and Meloe L. (地胆). He had also given the usage and efficiency of the drugs both for external application and oral administration. In the "Pharmacopoeia of the People's Republ ic of China" (1985), there are listed 10 different kinds of medicinal insects and their products, of which 2 species of Meloidae are included. In China, in recent years, the clinical practice of cantharidin and its derivatives proved that they have better curative effect on primary liver cancer and also on leucocytopenia, chronicliver disease, neurodermatitis etc. In order to conserve and also effect better usage of the natural resources of Meloidae, the authors have carried out an extensive survey of Meloidae from 1989 to 1991 in the following provinces, namely Hebei (including the outskirt of Beijing), Nei Mongol (Inner Mongolia) and Xinjiang in the north and Sichuan, Guangxi, Yunnan in the south. In three years, we ascertain that among the 35 common species of Meloidae in the afore mentioned provinces, there are 19 predominant species, namely Epicauta chinensis Laporte, E. Aptera Kaszab,E. tibialis Waterhouse, E. gorhami Marseul, E. hirticornis HaagRutengerg, E. kwangsiensis Tan, E. sibirica Pallas, E. dubia Fabricius, E. rufieeps llliger, E. megalocephala Gebler, Lytta caraganae Pallas, Mylabris calida (Pallas), M. Speciosa(Pallas), M. cichorii (Linnaeus), M. frolovi (Germar), M. Axillaris Billberg, M.Phalerata (Pallas), M. sibiriea Fischer and M. mongolica (Dokhtouroff). In order to determine the quantitative levels of cantharidin contained in the above species,chemical analysis of the dried bodies of adults were carried out by thin layer chromatography and gas chromatography methods (Tables 1 & 3). The results show that about 80% of the species containing cantharidin exceed 0.35%. The "Pharmacopoeia of the People's Replubic of China" stipulates that the blister beetles with no less than 0.35% of cantharidin can be used as medicine. So the present investigation greaty increased the number of meloid species to be used as medicine. The results also show that the cantharidin levels varies among different species and also among individuals of the same species collected from different localities. To this problem further investigation is needed. As a comparison, chemical analyses were also carried out on the dry bodies of Trichodes sinae Chevrolat and Huechys sanguinea (De Geer), the results show that both contain no cantharidin.