We in anticancer drug development from natural resources have conceived and used a wide variety of experimental screening systems to support our efforts during the past 20 tears. Screens have been devided to address targets at the molecular, biochemical and cellular levels, both in vivo and in vitro. Screens have been essential for the experimental evaluation of the products from natural sources. In this congress, antitumor screening methods for deveol[ment of new drugs from natural sources and evaluation of their crude drugs are discussed.