Bone remodelling occurs throughout life via the coupled actions of bone resorption and bone formation. When the balance of bone resorption and formation becomes unequal, bone diseases, such as osteoporosis occur, while the absence of functional osteoclasts leads to diseases such as osteopetrosis and pycnodysostosis. In order to develop effective treatments for bone disease the normal regulatory systems involved in bone resorption need to be fully elucidated. The only cell in the body capable of resorbing bone is the osteoclast - a highly specialized cell of haematopoietic origin. Until relatively recently, the ability to study the formation and function of human osteoclasts in vitro has been limited.In this chapter, we provide an up-to-date detailed guide to isolating and culturing primary osteoclasts from human peripheral blood. In addition, we detail the methodology used to characterize osteoclasts and how to quantify resorption in vitro. In combination these methods provide a powerful tool in the study of human osteoclasts and the development of new novel treatments for bone disease.