OBJECTIVE: To summarize the advances in the researches about cancer stem cells in last 5 years. METHODS: With the keywords "neoplasms, stem cell and cancer stem cells", 2 760 papers published from Jan 1979 to Dec 2008 were searched in the Pubmed databases. Adoptive standards: 1) the surface markers, drug-resistance mechanism and signal transduction pathways of cancer stem cells. 2) the origin of cancer stem cells. 3) cancer stem cells and clinical oncology. According to the adoptive standards, 33 top-quality papers were chosen for reviewing. RESULTS: Cancer stem cells have the properties of self-renewal and differentiation, with special cell surface markers and drug-resistance. The signal transduction pathways of cancer stem cells including Wnt, Notch, Hedgehog and Bmi-1 were abnormal. Cancer stem cells are the origin of malignant tumor's growth, recurrence and metastasis, having been the target of anti-cancer research. CONCLUSIONS: Rapid progress has been made in the research about cancer stem cells. The thorough study on cancer stem cells is significant for the diagnosis, treatment and prognosis evaluation of malignant tumor. The theory of cancer stem cells will change the current cancer diagnosis and treatment model.link_to_subscribed_fulltex