 Trial design : As a clinical trail aimed at studying the impact of anti-TNF treatment on osteoclastogenesis and osteoclast activity we will study one cohort of patients with RA before and at two points after beginning of the therapy, 3 and 6 months, so that each patient will be hisher own control beforeafter study. The two time points after introduction of the therapy are needed for two reasons : 1 The time when an eventual effect on the parameters studied may reach its peak is not known and 2 To assure that the parameters measured are stable over time. 