Fetuin-B, also known as Fetuin-like protein IRL685 and FETUB, is a secreted protein which belongs to thefetuin family. Fetuin-B / FETUB contains twocystatin domains. Fetuin-B is a member of the fetuin family, part of the cystatin superfamily of cysteine protease inhibitors. Fetuins have been implicated in several diverse functions, including osteogenesis and bone resorption. Fetuin-A has been identified as a major protein during fetal life and is also involved in important functions such as protease inhibitory activities and development-associated regulation of calcium metabolism and osteogenesis. Fetuin-A is a key partner in the recovery phase of an acute inflammatory response. Fetuin-B / FETUB is found at least in human and rodents. It is unambiguously a paralogue of Fetuin-A. Fetuin-A and Fetuin-B exhibit significant differences at the amino acid sequence level, notably including variations with respect to the archetypal fetuin-specific signature.