BACKGROUND India is a rich source of medicinal plants and a number of plant extracts are used against diseases in various systems of medicine such as Ayurveda, Unani and Siddha. Only a few of them have been scientifically explored. One of such plants is Ammannia baccifera L., traditionally used as an antitumor agent. OBJECTIVE The objective of the present study was to explore the anticancer activity of the methanol extract of A. baccifera against Dalton's ascites lymphoma (DAL)-bearing Swiss albino mice and in vitro cytotoxicity against human cervical cancer cell line (HeLa). METHODS In vitro cytotoxic effects of A. baccifera was evaluated against HeLa and NIH 3T3 cells using MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] method. Anticancer activity of the extract was evaluated in Swiss albino mice against DAL cell line at the doses of 100 and 200mg/kg p.o. The extract was administered to animals for 14 consecutive days. After 12h fasting from last dose, the mice were sacrificed and the anticancer effect of A. baccifera was assessed by evaluating tumor volume, viable and nonviable tumor cell count, tumor weight, hematological parameters and certain antioxidant biochemical parameters against DAL bearing control group. RESULTS The extract of A. baccifera was cytotoxic to the HeLa cancer cell line but relatively non-toxic to the normal cell line NIH 3T3. A. baccifera extract treatment resulted in significant decreases in tumor volume, viable cell count and tumor weight and enhanced the life span of DAL bearing mice. Hematological parameters such as RBC, hemoglobin and lymphocyte count reverted to normal level in A. baccifera treated mice. The extract also significantly (p<0.05) decreased the levels of lipid peroxidation and increased the activities of GSH, GPx, SOD and CAT. The anticancer effects of the A. baccifera extract is comparable with that of the standard drug 5-Fluorouracil. CONCLUSIONS The results showed that the methanol extract of A. baccifera is effective in inhibiting the tumor growth in ascetic models that is comparable to 5-fluorouracil. This plant has potential in the development of anticancer therapy and this study scientifically validated the folklore use of this plant.