Now, many anticancer drugs are applying in the clinical side, but there is no conclusive effect of such a chemotherapy. Development ofnovel clinical useful anticancer drugs would be dependenton the screen-ing system and its test sample sources. So, it is necessary to outlinesome background on the tumor systems which have been used for screen-ing. This paper describes mainely on National Cancer Institute (NCI)program for anticancer screening systems, because the large number ofcompounds have been screened at NCI prograB and their relationship ofassesment between experimental animals and clinical Patients has beendiscussing and the uniform screefing protocols for various tumorsystens. At the end of this paper, some literatures of antitunor substances from various higher Plants at our laboratory are showed.