AbstractActivin A, is a multifunctional cytokine of the transforming growth factor‐β superfamily of growth factors. This molecule has been shown to be implicated in the regulation of a broad range of important biological functions including bone remodelling. Therefore, a deregulation in the activin signalling pathway may result in disturbances of normal bone metabolism and, eventually, in the onset of severe pathological conditions associated with an altered bone resorption. These observations support the concept that Act A might also be implicated in the pathogenesis of bone metastasis. This review provides insight into the most recent advances in understanding the role of this growth factor in the pathogenesis of bone metastasis, and discusses the implications related to the biomedical applications of these findings. J. Cell. Physiol. 225: 302–309, 2010. © 2010 Wiley‐Liss, Inc.