Achyranthes aspera leaves have been assessed for chemopreventive activity. The MeOH extract, alkaloid, non-alkaloid and saponin fractions exhibited significant inhibitory effects (concentration 100 microg) on the Epstein-Barr virus early antigen activation induced by the tumor promotor 12-O-tetradecanoylphorbol-13-acetate in Raji cells. In this in vitro assay the non-alkaloid fraction containing mainly non-polar compounds showed the most significant inhibitory activity (96.9%; 60% viability). In the in vivo two-stage mouse skin carcinogenesis test the total methanolic extract possessed a pronounced anticarcinogenic effect (76%). The present study suggests that A. aspera leaf extract and the non-alkaloid fraction are valuable antitumor promotors in carcinogenesis.