Zinc is an essential element, necessary for sustaining all life. Zinc deficiency causes taste impairments, immune deficiency, skin problems, and growth and mental retardation. Recent reports suggest that zinc is associated with an increased risk of cancer, although it is still unclear whether zinc or its transporters are involved in cancer progression. Here we show that zinc and its transporter ZIP10 are involved in the invasive behavior of breast cancer cells. The screening of clinical samples for ZIP10 mRNA expression suggested that ZIP10 was significantly associated with the metastasis of breast cancer to the lymph node. In addition, the expression of ZIP10 mRNA was higher in the invasive and metastatic breast cancer cell lines MDA-MB-231 and MDA-MB-435S than in less metastatic breast cancer cell lines, such as MCF7, T47D, ZR75-1 and ZR75-30. In in vitro cell migration assays, the depletion of zinc transporter ZIP10 and intracellular zinc inhibited the migratory activity of MDA-MB-231 and MDA-MB-435S cells. These results showed that zinc and ZIP10 play an essential role in the migratory activity of highly metastatic breast cancer cells, and suggest ZIP10 as a possible marker for the metastatic phenotype of breast cancer and a promising target of novel treatment strategies. (Cancer Sci 2007; 98: 692–697)