The Ayurvedic system of medicine recommendsBacopa monniera(BM) in the treatment of tumors. The present study aims to determine the mode of cell death induced by the ethanolic extract of BM in mouse S-180 cells. BM-treated S-180 cells were assessed for cell viability in a dose- and time-dependent manner using dye exclusion studies. Morphological changes in the BM-treated and untreated cells were studied by transmission electron microscopy (TEM). Glutathione (GSH) levels were quantified and the percentage of apoptotic cells was determined using Annexin V-FITC assay. The results indicate that BM induces a dose- and time-dependent loss of cell viability with maximum cytotoxicity at 48 h at a concentration of 550 μg/ml. TEM studies indicate apoptosis in the BM-treated cells. GSH levels were decreased in the BM-treated cells and Annexin V-FITC assay revealed 90.2% of the cells as apoptotic. Conclusively, BM induces cell death by apoptosis in S-180 cells. Copyright © 2008 John Wiley & Sons, Ltd.