In the present investigation the topical application of single dose of DMBA followed by croton oil induced the skin papillomas in all the animals by the 15th week. Cumulative number of Papillomas and tumor yields were recorded as 28, and 4.6 respectively. Whereas the animals which received Bacopa monnieri extract additionally at the dose of 200 mg/kg body weight, the cumulative number of Papillomas, tumor yields were recorded as 18 and 3.0 respectively and these were observed to be significantly lower than DMBA+Croton oil group. In another experiment, B16F10 melanoma propagated by subcutaneous injection of 106 melanoma cells on the dorsal skin of C57BL mice. The tumour growth and tumor volume of cyclophosphamide treated by subcutaneous route at single dose of 300 mg/kg body weight, 30 min. after tumor cell inoculation the tumors size was significantly reduced and inhibited the tumors growth by 46.74 %. Whereas when cyclophosphamide was given at single dose and Bacopa monniere extract was given for 21 days by oral route, the tumor size was further reduced and tumor growth was inhibited by 50.71%. However Bacopa monniera ext. alone treatment (200 mg/kg oral 21 days) the tumour volume was also reduced and tumor growth was inhibited by 27.27 %. It seems that Bacopa monnieri extract in combination with cyclophosphamide has significantly prevented the tumour volume as compared to control. In antimutagenicity studies Bacopa monnieri administered i.p. at the dose dependent manner have inhibited micronucleus formation and chromosomal aberrations induced by known mutagen in Bone marrow cells of Swiss albino mice. It is therefore concluded that Bacopa monnieri extract has anticarcinogenic and antimutagenic activity in the above test systems.