UNLABELLED: Cancer is a very important national health problem in Mexico, while a significant increase in the total and childhood cancer mortality has been recorded during the last decades. Chemoprevention, defined as the use of natural or synthetic agents to prevent or to block the development of cancer in human beings, is a new and promising strategy in the battle against cancer. Saffron, obtained from the dried red-dark stigmas of Crocus sativus L., an important spice rich in carotenoids, is commonly consumed in different parts of the world and used as a medical drug to treat numerous diseases. OBJECTIVE: To test the toxicity of saffron extract in vivo; to separate different ingredients in saffron extracts; to examine the cytotoxic effect of saffron and its main components on the growth of different human malignant cells in vitro; to evaluate the mutagenic and antimutagenic activities of saffron extract. METHODS: HPLC with photodiode-array detection was used for semi-preparative separation of different ingredients of saffron crude extract. Colony formation assay was used to determinate the cytotoxic activity of saffron extract and its components on human tumor cells in vitro. Mutagenicity and antimutagenicity assays were performed by the Ames method. RESULTS: Saffron is not toxic, non-mutagenic, non-antimutagenic and non-comutagenic. Twelve components were isolated: crocin-1, crocin-2, crocin-3, picrocroein, acid form of picrocrocin, HTCC-diglycosil-kaempferol trans-crocin-4, trans-crocin-2, trans-crocin-3, safranal, crocetin and cis-crocin-3. Saffron extract itself and some of its ingredients displayed a dose-dependent inhibitory activity against different types of human malignant cells in vitro. HeLa cells were more susceptible to saffron than other tested cells. CONCLUSIONS: Taken together, our results and literature data indicate that saffron could be used as a potential cancer chemopreventive agent in clinical trials.