Alcoholic extract of Acanthus ilicifolius (250,500 mg/kg b wt) was found to be effective against tumour progression and carcinogen induced skin papilloma formation in mice. The extract was found to be cytotoxic towards lung fibroblast (L-929) cells in 72 h MTT assay and the concentration required for 50% cell death was 18 microg/ml. Oral administration of the extract (500 mg/kg b wt) reduced the tumour volume and administration of the same concentration increased the life span by 75% in ascites tumour (EAC cells) harbouring animals. The extract also significantly delayed the onset of dimethylbenzanthrazene DMBA/Croton oil induced skin papilloma in mice in a dose dependent manner.