Antitumor activity of saffron (Crocus sativus) extract a commonly used spice in India was studied against intraperitoneally transplanted sarcoma-180 (S-180), Ehrlich ascites Carcinoma (EAC) and Dalton's lymphoma ascites (DLA) tumours in mice. Oral administration of 200 mg/kg body weight of the extract increased the life span of S-180, EAC, DLA tumour bearing mice to 111.0%, 83.5% and 112.5%, respectively. The same extract was found to be cytotoxic to P38B, S-180, EAC and DLA tumour cells in vitro. Thymidine uptake studies indicated the mechanism of action of the extract at the site of DNA synthesis. Toxicity studies showed that the hematological and biochemical parameters were within normal range. These results indicate the potential use of saffron as an anticancer agent.