The fact that, of the approximately 600,000 plant species existing on the earth, only some 5 % have been specifically investigated chemically or pharmacologi cally, is a challenge to chemists spezializing in na tural substances and to pharmacologists. In view of the limited number of research capacities and the ever diminishing financial means, this challenge can only be met if, together with an improvement and refinement of methods of analysis, medicinal plant research is carried out on a broader interdisciplinary basis, with comparable, scientifically recognized screening methods, and if it is better coordinated, with greater use of modern documentation means. It is thus necessary in the future to concentrate specifically on projects leading to the development of new medicinal prepara tions. The plenary lectures hold in the present symposium of the 1st International Congress for Research on Medi cinal Plants reflect these efforts and tendencies. At the same time they provide a survey of some of the fields of medicinal plant research which are at present most actual and most intensively researched. They range from plant screening, isolation and structure eluci dation of new principles, to the therapeutical opti mization of a natural product. The lectures given at this congress show clearly the necessity, in addition to national phytochemical so cieties, for a central international organisation, in which all active medicinal plant researchers in the world are included. Their aim should be to provide the impulse for more optimal, rational research, aimed at the solution of specific projects.