Ginger (Zingiber officinale Roscoe, Zingiberaceae) is a commonly used medicinal herb throughout the world. Although some studies have demonstrated its antitumour activities on cancer cells in vitro and in vivo, the exact mechanism is not fully elucidated. Hence, the present study was designed to examine the in vitro cytotoxic activities of saline extract prepared from ginger extract on HEp-2 cell line. The cytotoxic effect of the drug was confirmed by 3-(4,5-dimethyl thiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay and cell counting and estimation of protein, DNA and RNA. Meanwhile, propidium iodide staining and agarose gel electrophoresis were performed for determining the induction of apoptosis. In addition, superoxide radical generation, nitrite formation and glutathione studies show involvement of free radicals. The present results show that the extract exerts dose-dependent suppression of cell proliferation; the IC(50) value was found to be 900 microg/ml. At a dose of 250 microg/ml, marked morphological changes including cell shrinkage and condensation of chromosomes were observed. Agarose gel electrophoresis of DNA from HEp-2 cells treated with 250 microg/ml ginger powder for 24 hr showed marked DNA ladder pattern. The involvement of free radicals was confirmed by increased superoxide production, decreased nitrate formation and depletion of glutathione in ginger-treated cells. Further screening of active components using gas chromatography-mass spectrometry analyses showed the presence of clavatol, geraniol and pinostrobin in the extract. The results of the present study suggest that ginger might be useful as a potential antitumour agent.