A new approach to cancer therapy in recent years has been to target the metastatic process. The anti-metastatic potential of curcusone B, a diterpene isolated from Jatropha curcas Linn. (Euphorbiaceae), a herbal plant that has been used in traditional folk medicine in many tropical countries, was investigated against 4 human cancer cell lines. Treatment with non-cytotoxic doses of curcusone B resulted in a strong reduction of in vitro invasion, motility and secretion of matrix-metalloproteinases (MMP) of the cancer cells, whereas the ability to adhere to a Matrigel-coated surface was variably sensitive to curcusone B treatment. Curcusone B, thus, effectively suppresses the metastatic processes at doses that are non-toxic to cells, which may be of therapeutic benefit for the treatment of metastatic cancers.