Mentha arvensis (MA) commonly known as Mint or Pudina, belongs to the Lamiaceae family. It is an aromatic herb traditionally used as an antiseptic, anthelmintic, diuretic, digestive, expectorant and cardiotonic. In the current study, the in vitro cytotoxic activity of Mentha arvensis whole plant crude extracts was evaluated by Sulforhodamine B assay on three human tumor cell lines from different tissues, namely A-549 (lung), MCF-7 ( breast) and COLO-205. (colon). The methanol extract of Mentha arvensis was observed to be significantly more cytotoxic in a dose-dependent manner than the petroleum ether extract of Mentha arvensis with IC50 ranging from 120 to 165 µg/ml for the selected cell lines. The haemolytic activity on human red blood cells was also checked. Crude MA extracts were found to have no hemolytic effect on red blood cells, suggesting that membrane destabilization is not the mechanism of action. The study therefore suggests a potential anti-tumor activity of Mentha arvensis and the need for further studies to identify the active components and understand their mechanism of action. Keywords: Mentha arvensis, Antitumor Drug Screening Assays, A549, MCF-7, COLO-205Mentha arvensis (Family- Lamiaceae) is an erect, branched, strongly aromatic herb, with stems up to 75 cm long. The leaves are elliptical to oblong-ovate, 5 cm long, with short petiole, toothed margins, rounded or blunt apex. The plant has lilac to blue hairy axillary flowers[1]. It is commonly known as "Pudina", "Mint", "Wild Mint" or "Corn Mint". Although it is mainly found in the western Himalayas, it is cultivated throughout India. According to Indian Ayurvedic medicine, Mentha arvensis is used as an antiseptic, anthelmintic, diuretic, antispasmodic, stimulant, gastric, carminative, digestive, emmenagogue, expectorant and cardiotonic. It is useful in ulcers, wounds... middle of paper... The haemolytic activity on erythrocytes has also been studied for extracts with methanol and petroleum ether of Mentha arvensis. Total hemolysis was achieved using 100 μl of sterile D/W solution after three hours of incubation at room temperature. The test extracts did not possess any hemolytic activity against erythrocytes (Table 2). The lack of hemolytic activity suggests that crude MA extracts protect the biological membrane and therefore membrane destabilization is not the mechanism by which it kills tumor cells[17]. The cytotoxic activity of MA oil has already been reported on MCF-7 and Lan-CAP cell lines by Husain et al.[18]. The present study reports for the first time the in vitro cytotoxic activity of subsequent methanolic extracts of MA on tumor cell lines suggesting its potential antitumor activity. Therefore, further studies are necessary to identify the active ingredients and understand the mechanism of action.