Green tea is a popular beverage in China and Asia and has been shown to possess antipyretic, diuretic and several other pharmacological activities. The major constituents of green tea are polyphenols which have been found to possess antioxidant and antimutagenic properties. In this study green tea polyphenols (GTP) were evaluated as an anti-initiating agent against the skin tumorigenicity induced by polycyclic aromatic hydrocarbons (PAHs) in mice. In a complete skin tumorigenesis protocol using 3-methylcholanthrene the topical application of GTP to female BALB/c mice resulted in substantial protection against the onset and subsequent development of tumors. In the two-stage skin tumorigenesis protocol using 7,12-dimethylbenz[a]anthracene (DMBA) as the initiating agent followed by twice weekly applications of 12-O-tetradecanoylphorbol-13-acetate; (TPA) as tumor promoter, topical application of GTP to female SENCAR mice afforded significant protection against skin tumorigenicity. Oral feeding of GTP in drinking water to female SENCAR mice also protected against skin tumorigenesis in DMBA - TPA-treated animals. GTP when administered topically or orally significantly inhibited PAH - DNA adduct formation in epidermis after topical application of [3H]benzo[a]pyrene or [3H]DMBA. Our results suggest that GTP has substantial anti-skin-tumor-initiating activity against PAHs and could prove useful in protecting against some forms of human cancer.