 Osteoclastic bone resorption depends on both the capacity to generate osteoclasts osteoclastogenesis and on individual osteoclast activity. Our objective is to study the effect of anti-TNF therapy on the number of osteoclast precursors in the peripheral blood of patients with RA, on in vitro osteoclastogenesis and on osteoclast activity before and during the treatment of patients with RA with Adalimumab. 