Present anticancer drugs in the clinical side have not showed a conclusive effect of the chemotherapy for cancer patients. In order to find much more efficient antitumor agents fromnatural resources, various screening methods vivo and in vitro have been developed by manyresearchers. The intention of this paper is to provide an outline of some background on the tumorsystem in drug development of natural products, to review some screening programs for theevaluation of antitumor activity and to introduce the practical procedures of some antitumorscreening methods in vivo and in vitro. At the end of this paper, the current literatures related toantitumor natural products from higher plants at our laboratory are described.Key words'anticancer drugs, screening methods.